Thoughts on the subject from T. Rowe Price:
There is no set definition for what makes a concentrated position. When an investment in a single stock represents more than 5% of a portfolio, T. Rowe Price advisors consider it to be worth addressing. Once a holding exceeds 10%, however, it represents a greater risk that requires more immediate planning. “Most situations we see aren’t in a gray area, however,” says Daniel Tafoya, CFP®, a financial planner with T. Rowe Price. “Clients with concentrated positions often have 20% or more of their portfolio invested in a single company. This level of concentration is clearly a concern.”
Source: https://www.troweprice.com/personal-investing/resources/insights/actions-can-take-if-your-portfolio-is-too-concentrated-in-one-equity.html

Perhaps my memory of what was notarized at the local UPS stores near me is flawed. I'm pretty sure I got two medallion signature guarantees at one of them.
I can say one thing for sure: maybe 12 years ago local banks stopped being a sure bet for medallions. They went from Any Time You Wish Sir, to once a week, to a haphazard schedule to none. And when it got to None they sent me to Any Notary Public. And I found one a block or two from the bank. She was not a financial institution officer. And she charged me an exorbitant fee. But I got the medallion signature guarantee in her little office.
Here is a link to info about what UPS notarizes:
https://www.theupsstore.com/store-services/notary-services
It looks like wills and trusts are included at at least some of their branches.
No mention of medallions.

Notary & Signature Guarantee
Notaries just require state registrations/licenses to operate. Some get it for earning extra income on the side. Many currency exchanges have notaries. Many legal offices have someone on staff as notary. All a notary is vouching is that the signature belongs to the one signing it (in front of them) - there is no liability beyond that (and any liability would be the loss of registration/license).
Signature Guarantee is same as Medallion Signature Guarantee. It is by bank or financial institution officer. Beyond authentication of signature, there is also financial liability about the soundness of the document being guaranteed. In some Signature Guarantees at my local bank, I have gone through almost half-hour interview process on what/why I am doing something. Once for a 529 signature guarantee, the guy thought something looked strange, and he called the 529 program right away to determine if what I was doing was allowed by them. Good that I had prior related correspondence from the 529.
It's a long way of saying that I doubt some kid at the local FedEx or UPS store can do Signature Guarantee.

Yup. That's where I go when I need a medallion signature or something notarized.

Not a single neighborhood financial institution, brokerage or bank, has a notary anymore (I checked a month ago).
Maybe because some kid is doing it at the local FEDEX/UPS store.

Not a single neighborhood financial institution, brokerage or bank, has a notary anymore (I checked a month ago).
Maybe because some kid is doing it at the local FEDEX/UPS store.

The nearest Fidelity office is four miles from my home. There is no parking whatsoever around there.
My nearest Fidelity office is nearly 4 miles away, over in the next county. Not only is parking nonexistent, but the drive alone would take around a half hour on a good day (an hour is more realistic). Not in a million years would I drive to a nearby Fidelity branch. (Some branches two counties and a 1¼ hour drive away have parking lots.)
These days many urban areas have bikeshare systems for short, one-way trips. No need to own a bike.
https://data.bts.gov/stories/s/Bikeshare-and-e-scooters-in-the-U-S-/fwcs-jprj/
I can still count on Fidelity for notary and medallion guarantee services. Not so for the Schwab office four blocks from me or the neighborhood BofA/Merrill. They'll both just send the papers over to a back office somewhere for a medallion stamp. Not a single neighborhood financial institution, brokerage or bank, has a notary anymore (I checked a month ago).
Those four miles are looking better and better :-)

I invest mostly in mutual funds and ETFs but do own one individual stock.
I prefer to limit individual stocks to ≤ 5% of my total portfolio.
This offers protection against potentially large losses from overly concentrated positions.
Extremely concentrated equity positions were a significant factor
in achieving wealth for some of the richest people on earth.
With that said, I don't expect to join the billionaire's club but hope to achieve more moderate financial success.

Thank you, @Mark One may buy 'cheaply' the book, 'The Millionaire Next Door'. Yes, income is very important, but so are spending habits. I will admit this book and its methods, don't help the ultra poor.

Quite right. You could have eighteen bazillion dollars and be foolish with it, and lose it all. That happens to celebrities often enough. I knew a guy who trusted his accountant TOO much. Never checked the 1040 for himself. He was beholden to the IRS for a helluva lot of money, over a period of years and years.
And if you're very poor, the savings and investment techniques which require the use of MONEY YOU DON'T HAVE are useless. But the school systems truly ought to be teaching financial literacy. Not in order to make students all excellent and talented capitalists. Yet, capitalism is the only game in town--- apart from a hybrid economic arrangement like they have in Scandinavia. (Where poverty and homelessness are not such a scourge, as in the States?) And people DO invest in Scandinavian countries, eh?

Well now I know. The letter says Corebridge Financial (formerly, in my case, AGI VALIC) is the source of the data breach that includes me. This is an old 403b type plan from my days at University of Texas. The letter seems to be the same as others have described with the same credit watch and advice. Thanks all for your input.

@Crash- do you really think that financial games and "gotchas" started with "capitalism"?
Do you really think that in today's world non-capitalistic financial systems don't do this stuff?
Do you really think that the early Genoese and Venetian traders never did this stuff?
Do you really think that all of the European and Mediterranean trading empires didn't do this stuff?
Do you really think that whatever trading occurred before all of those guys didn't do this stuff?
Do you really think that since mankind first traded flint arrowheads, seashells or whatever those guys didn't do this stuff?
Get real.

@ Anna
I am sorry your husband passed. It seems most of the posters here seem to be men, and women have less interest in trading/investing.
My wife is similar and rivals Buffett, as she would never sell anything, (including CSCO in the 80s in 2000!)
While I am healthy and only recently retired, Charles Lynn Boylin's posts about setting up a simple "Glide path" for his wife if he gets hit by a bus is a useful reminder that we need to think ahead.
We have had our data hacked many times. Three times at Yale New Haven Hospital alone; twice by BC/BS. OPM from USGOV. A hard disc with all out unencrypted account information from a bank we used was "lost" in the back seat of a taxicab.
The most egregious was the Equifax hack.
It goes on and on.
@catch22 see link below
TIAA hired an entity called PBI, a vendor that provides search tools to financial services institutions such as TIAA, the suit states. PBI, in turn, hired PSC, a software company, for the storage and transfer of TIAA’s client data entrusted to PBI.
PBI uses PSC’s MOVEit file transfer services for a variety of purposes, including the transfer of Plaintiff’s and Class members’ personal data.
https://www.thinkadvisor.com/2023/08/08/tiaa-hit-with-class-action-suit-over-moveit-hack/

It is kinda a pain to set up though

Yes, after my husband died, I had to report it to all the credit agencies. Supposedly, all you need to do is report it to one and ask that one to report it to the others. So, I sent a letter and the relevant documentation to TransUnion with the request that they report it to the others. I also requested a final credit report for him. They said they reported his death to Experian and Equifax but not the request for a final report. I requested the final reports from the other two and they would not give them to me without jumping some hoops. When I asked that they verify that TransUnion had reported his death to them, one didn't answer and the other said he was sure that if I asked that it be done, it must have been, but he wouldn't check for me. I gave up.
Like you I am a member of numerous breaches, including a couple of federal government ones and State of Delaware ones. I have been on many watches and will join another if invited. Honestly, I find these companies provide more information on my neighborhood predators than on my ID or financial stuff. I hate it because each time it is a different company, and the company wants all my personal and financial information. Which, to me, just creates a centralized list of all the information on me. What a break-in that would be if all MOVEIT personal info were breached!
Thanks.

I also have a password protected word file on my computer and no where else ( except hard copy in Safe Deposit box for financial passwords. I copy and paste them into the web page login.
Less important stuff I use 1Password which works OK. There are some places it will not "autofill"
I used LastPass until they were hacked twice
No identifying documents in cloud storage

@sma3
I started out many years ago using Vanguard's free financial planning tool. I think it might have been Financial Engines. I later created my own spreadsheet financial planning tool.
My employer moved our accounts to Fidelity, and I started using their financial planning tool many years ago and really liked it. Several years ago, I began using Fidelity's services from my employer which was essentially a financial planner for providing advice, but not managing my accounts. To my surprise, he used the same Fidelity Planning tool that I had already set up. Now that I use Fidelity Wealth Management, we have still reviewed the financial planning tool.
Yes, there are a few unknowns about it. It provides estimated end of plan assets but does not display tax planning options such as Roth Conversions. I still use my planning spreadsheet which takes into Roth Conversions and accelerated withdrawals, but it supplements Fidelity's tool.

Motivated by Lynnbolin's review of Vanguard advisory I poked around at Vanguard and Fido planning and advisory groups.
I did not know of Fido's free financial plan process, but it is very robust and useful.
It will calculate income, expenses, investment returns and RMDs and you can tweak your asset allocation specifically by each of your accounts including non Fido ones.
I do not know what assumed rate of returns they use for each asset class, and unfortunately they don't seem to tell you, although they will suggest an allocation for you based on the usual risk tolerance questions.
It is worth taking a good look at. The only think similar I know of ( without a fee) is Quicken's old planning feature, but they have not updated the RMD dates yet.
I don't know if Vanguard or Schwab offer similar services but will take a look. From what I can see Schwab offers a plan for $300 and $30 a month.

In response to several comments above:
I have been a DIY investor until about two years ago. I did try the Charles Schwab robo-advisor. I have been using both Fidelity and Vanguard for decades and like them both for different reasons. I now use the Fidelity Wealth Services and Vanguard Personal Advisor Service Select.
For clarification, Vanguard Advisor Services are:
1) Robo Advisor Services with a minimum of $3,000:
https://investor.vanguard.com/advice/robo-advisor
2) Personal Advisor Services which is a hybrid robo advisor with a minimum of $50,000 and team of advisors. Cost is 0.35%:
https://investor.vanguard.com/advice/personal-hybrid-robo-advisor
3) Personal Advisor Services with a minimum of $500,000 and a personal certified financial planner/fiduciary in addition to the team. Cost is 0.3%:
https://investor.vanguard.com/advice/personal-financial-advisor
Fidelity Wealth Management fees are listed as 0.50%–1.50% with a minimum of $250,000. The more you have them manage the more your fees fall.
I invested the minimums to get a personal advisor and to lower my fees.
With regards to objectively evaluating the funds and services:
Whether you work with Fidelity or Vanguard, they will evaluate your goals and needs and propose an allocation (or range) and the funds. Both base their recommendations on the long term, but Fidelity also adjusts based on the business cycle. You can make changes within their criteria and policies. I entered the funds and allocation into the MFO Portfolio Tool to evaluate them. With Vanguard Advisor funds being only 1.7 years old there is not much history to go on. Vanguard has the option to select the percent of active and passive funds.
With a dual income household, we have multiple accounts with different tax characteristics. Our advisory service ranges from 50% stocks to 70% based on my input.
With regards to performance:
It does take a leap of faith to use an advisory service. There is evidence that individual investors tend to underperform the markets because they tend to panic, trade too much, or be too conservative. I did take the leap of faith based on my experiences with both Fidelity and Vanguard.
My primary objective is to set my wife up with a financial advisor in case I pass away before her. Mission accomplished. The surprising thing is that I feel a burden is lifted and more relaxed. I still have accounts that I manage myself.

Don't let names of services confuse you. PAS at Vanguard and PAS at Fidelity are two different animals. PAS at Vanguard is a hybrid robo advisor, similar to Fidelity's GO (assuming AUM of at least $25K). Fidelity defines the service this way:

A hybrid robo advisor typically refers to a robo advisor that includes access to investment adviser representatives, whether via telephone or in person. In the case of Fidelity Go®, we combine our digital offering with access to 1-on-1 financial planning and coaching via telephone for clients that invest at least $25,000 in a Fidelity Go account.

https://www.fidelity.com/managed-accounts/fidelity-go/overview
The cost of Fidelity GO is 35 basis points/year. But the account uses Fidelity Flex funds, which have ERs of 0.00%. Vanguard's PAS uses Vanguard funds. So the all-in costs of these two services should be similar.
Fidelity's older PAS service uses proprietary and third party funds. It is model based but not robo-based. The last time I looked at it many years ago, it tended to throw a gazillion funds into a portfolio, perhaps because it could, perhaps because that gave the impression that it was doing something. In any case, this is not the same type of service as Fidelity GO or Vanguard PAS.
https://www.fidelity.com/managed-accounts/overview
https://www.fidelity.com/wealth-management/investment-management-services
FIdelity has so many fee schedules that it's hard to find the one you're looking at. Their fees are different for Fidelity-preferred portfolios, "blended" (no preference) portfolios, and index fund portfolios. Regardless, PAS services do cost much more than hybrid robo services, whether at Fidelity or elsewhere.

@lynnbolin2021
Thanks again for the hard work on all this.
Am I correct that you have advisory accounts at both Fido and Vang?
Do you still have significant % in the other fund strategies you have written so much about? If so I assume those accounts are completely separate from the PAS
It appears Fido wants you to pick an individual advisor to use from their long list, while Vanguard assigns someone to you after you go through their allocation questionnaire. Is this accurate?
Have you found their "financial planning " process useful?

FWIW
I looked into Fidelity's service. I am sure Lynn knows more about it than I found in an hour or so of searching around, and I would be interested in his experience.
Using what appears to be their fee schedule, Fido is much more expensive than Vanguard. They charge 1.25 % on the first $500,000. on a $6,000,000 account even with the declining fees, the total works out to 0.46% vs Vanguards flat 0.3%. To get pricing similar to Vanguard's it looks like you need to have $10 million in total investable assets or net worth.
There is little discussion of how they pick investments, as it is all managed in house by their advisors. A quick look down the line of folks offered up to help does not indicate they are anything special. Without a personal recommendation from someone you trust with experience at Fidelity, you are probably just as well off with a robot!
It does not appear that either place offers financial planning or asset allocation advice without committing to investment management.

A program isn't a fiduciary. The RIAs (Registered Investment Advisors) are fiduciaries.
So, a RIA handling PAS (or other financial stuff) will be a fiduciary. The RIAs need Series 65, or Series 7 + 66, exam(s).
A call center employee (needing only minimal training) or broker or insurance agent handling PAS won't be. Brokers only need Series 7 exam. Insurance agents need relevant insurance exam(s).
The financial industry is trying to fuzzy things up by also creating Regulation Best-Interest (Reg BI) for the non-RIAs, something in between the requirements/standards for brokers and RIAs. It isn't just practical or possible for everybody to qualify for RIAs overnight.