I got hooked on looking for these a few years ago when a fellow collector shared his set of mercuries that he had accumulated over the years. Yes, a complete set of Mercs like the following.

Notice the ring in the center of the coin, yea I know, its an 1896S, what a shame. This ring was caused by a littel silver bank people used to use to save up a roll of dimes. The top coin when compressed would get the special ring. What does this bank look like? Well, I have also purchased one of them for my little off the wall collection and thought I would share that with you as well. Notice the little knob on the top? its a little screw that keeps the dimes in the bank so they don't fall out. Watch at flea markets for these.. I paid a buck for mine. : )

Can you imagine what the odds are of completing a full set of dimes that had been the top dime in one of these banks? WOW