I was realized something. How is it possible to have error coins with like a D and an S error coin that has 2 different mints together like a D over S? Don't the letters stand for where it is made? If they make them in philidelphia, denver san francisco, and other places, why would they have something that could make D coins and S coins in the same machine? I am starting to think that they make all coins in just one place.
Well "somebody" the dies are all made at the same place and I believe it is Philadelphia. So lets say you are currently striking new quarters at Philly and your obverse die cracks so bad it can't strike another coin. You go to the die room (tool room or whatever) to get another die and there are none ready with the Philadelphia mint mark but there are a few for Denver and San Fransico lying there? Well you fill the mint mark that has already been punched D or S and repunch it with a P. You are set to go! After striking a few hundred or perhaps thousand coins the filler you used on the other mint mark breaks loose and now you have a P over D or S (which ever mint mark you filled). Used to happen quite often as dies are very expensive to make and a little old mint mark was easy to fill and repunch. Basically mint official did what ever they had to do to keep production going so using a die with another mint mark was not out of the question if that is all they had to work with. Fill it, repunch the mint mark and your back in business! Also there are ocassions when the wrong dies may have been shipped to the wrong mint and if keeping on a schedule meant filling and repunching a mint mark...well they did just that as years ago things didn't get shipped over night so there were no other options. Hope this helps you to understand how the errors could occur.
I've never heard of filler being used - but they certainly did re-punch the mint marks - usually right on top of the old one.
