there was a discussion about this same moral issue a couple of months ago and the general concensus is that the lucky buyer really should take it back and explain its value and rareity. she may tell you to keep it for the price paid. personally i think it should go back to the ex husband.
he may have his brains in his trousers, but thats no reason for him to be ripped off and lose such an iconic watch.
just my 3.8c
Graham