I did make a successful claim on the Marshall Farms guarantee back in
1999.  It was for a deaf ferret.  I needed a vet's certificate stating
that he was indeed defective aka deaf.  Marshall gave me a choice of
trading in the ferret or a credit for 1/2 his purchase price at the store
where I purchased him.  I used the credit for a bunch of ferret supplies
that I donated to the local shelters through the ferret club I belong to.
 
Hope this helps.
 
Kristeen-NJ
[Posted in FML issue 5133]