Why would a business customer use a stamp of their signature. First, a business cannot sign its name, only a person can sign their name. Businesses usually endorse their checks with an endorsement stamp that says "for deposit only".
Whether or not they endorse the checks at all does not change the fact that you warrant to all future endorsers that the proper party got the benefit. If that did not really happen, you will get the check back and have to be made whole by your customer.
I must be confused by your question.
Al
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Al Miller, CRCM
Opinions expressed are my own and not necessarily shared by my employer.