While going through some coins, I noticed how the location of the D mintmark on one penny, was higher than another. Take a look: Notice that the mintmark of the 85D is much lower. Is this an error or is it just so because of die alterations?
Mintmarks used to be manually punched into the dies, so the MM can have different positions not only year-to-year, but within one year. On key dates, this is a great tool used to certify the coin as legitimate, and not as a modified date, added mintmark, counterfeit, etc.
Beginning about 1990 the Mint placed mintmarks on the original model so the mintmark is on the Master Hub all the way down to the Working Dies. That means that every Working Die has the exact same mintmark in the exact same location. Before about 1990 the mintmarks were punched into the Working Dies by hand so there was some natural variaton in mintmark location, orientation, punched depth, etc.
"The Authoritative Reference on Lincoln Cents" - this book explains how this all plays out really well including how this manual process produced a great many omm's.
I was totally baffled by this when I began collecting. I hoped I found some great rarity...but no such luck.
