I was in the supermarket the other day and I found a credit for the supermarket. could I keep it? It was in Jerusalem.
Answer:
This question is particularly interesting. There are a number of issues involved.
Firstly, since the credit note is found in a place which is open to all, the first person who picks it up gets it and not the storeowner in whose domain in was found.
However, can the finder keep it? Well, if it has a siman - an indentifying mark or sign - then we can assume that the owner who lost it will not give up hope of getting it back, since he can declare the siman to the finder and thus prove it was his. Althought the credit note itself has no identifying marks, the amount of the note may well itself be a Siman.
Even if we asssume that it has no siman, and thus the owner would have given up hope of getting it back, although usually a finder under such circumstances may keep the lost object for himself, in this case it may be different. This is because in effect a credit note for a store is a kind of Shtar chov - bill of debt. What happens if someone loses a document of debt and gives up hope of getting it back?
Fistly, if someone gives up hope of getting back his shtar and thus of claiming his debt or credit, does that mean that the borrower (or store) no longer owes him the money?
Furthermore, even if we were to decide that the owner or lender actually loses the right to claim under such circumstances, can a finder claim with the debt with the shtar or credit note? Perhaps do we say that as soon as the lender gives up hope and relinquishes his ownership of it, the first person to "acquire" the debt is the borrower himself - if the lender has no possibility of claiming it then the borrower owes noone anything, and thus even is someone subsequently picks up the bill of debt or the credit note there is nothing for him to actually acquire (other than the paper for its value as a piece of paper, not its value vis-a-vis the debt therein).
These points are a matter of considerable debate amongst the later Halachic authorities (see Ketzos, Nesivos, Urim VeTumim et al at the beginning of Choshen Mishpat Siman 66), and it is difficult to rule conclusively, and as such it is difficult to sanction going ahead and using the found credit note in the store.