A customer has two checks to deposit in their joint account, one is stamped 'for deposit only' and the other is not. The customer wants cash back from the deposit. Since the second check is endorsed and is not stamped, is it permissible to give cash back and have the customer sign the front of the deposit ticket for receiving the cash back?

Why don't you just ask them to endorse the check?

On the second check what type of endorsement was it?

The first check is payable to the husband and was stamped "for deposit only". The second check was payable to the wife, who was there making the deposit to their joint account. She wanted cash back which did not exceed the amount of her check. Her check was endorsed by her.

Seems perfectly fine to me.

That seems OK to me, just have her endorse the back of the check that she is getting the cash from.

Have her sign the acknowledgment of receipt of the cash back on the deposit ticket. The check payable to the husband is technically not indorsed, but you don't need an indorsement to take it for deposit since it's going into his (joint) account. UCC 4-205

As mentioned, the stamp for deposit only is not an endorsement it is a restriction.