If the payor has not signed them, they are not valid or negotiable instruments. If the checks are payable to another person, you have no legal right to use them. If you attempt to sign or endorse them to yourself or someone else without right, it will be forgery, which will expose you to civil and criminal liability. Checks are generally not like cash, they are more like promissory notes, in that they are a promise to pay a certain amount. However, there are certain situations when checks can be treated like cash, and your situation does not appear to be one of them.
However, you should speak with an attorney familiar with commercial paper/banking to assist you further. After a quick review, the attorney should be able how to tell you how to dispose of them.
If this response was helpful, please mark it as helpful or as a best answer. The response provided herein is for informational purposes only and is not intended as legal advice, nor does it establish or intend to establish an attorney-client relationship. You should always speak with a licensed attorney regarding your legal rights before taking or not taking any particular action.
Brokerage firm checks generally do not look like this, especially if they're drawn on a local bank. There have been a few cases where a wayward broker will open an account in the name of his brokerage firm, usually for improper investments or other clandestine purposes. You should send the checks to E-trade and explain the circumstances in which they were found. More likely than not, the former owner of your storage unit was engaged in fraud of some kind
The foregoing is not legal advice nor is it in any manner whatsoever meant to create or impute an attorney/client relationship.