Nice coin. I found a 1941d 10c unc FSB, from a store last year, so keep your eyes open. When times get bad, they (old coins and old currency) start popping out. It also, could be from a person's collection that was taken by a child, or stolen. Also, last year at the bank I go to, one of the tellers ask me to look at a coin that she got for face value, it was $20.00 gold coin (Indian)AU, becuae the kid or guy, could not get anyone to take it, so she gave him the $20.00 in FRN, so hes could buy something.
Silver dimes weigh 2.50 grams and cupro-nikel ('65 to date) dimes weight 2.27 grams. Most vending machines sort by weight, diameter and magnetic properties. Steel is rejected automatically. Nickel has some magnetic properties and is incorporated in AlNiCo magnets (Aluminum, Nickel and Cobalt). As far as I know, Silver doesn't have the same magnetic signature as Nickel. So, weight would be the key factor in rejecting silver coins as all coins that were made of Silver that have been replaced by clad versions have a different weight. Check your Red Book where it gives the specifications for each coin if you have any doubts.