Can a check that has the phrase "Subject to STA TOD Rules" be cashed out...?

Did you ever figure this one out?
We'd never seen a check like this until today

Is the check issued in payment of dividends on stock or the redemption of stock or other securities? (Properly used "STA" means Securities Transfer Association.)

It's often the case that checks issued as dividends or other payments from brokerage accounts (as well as those issued by banks for interest payments from deposit accounts) are printed with payee and address information that exactly duplicates the account registration information on the issuer's system. So, if Ken has hit on the actual abbreviation involved, the account from which this check was issued was probably a securities account designated for transfer on death to a designated individual or individuals.

It's my understanding that things like "STA TOD" or "POD [name]" are extraneous and don't affect ownership or negotiation of the check.