I'm trying to get a better understanding of certain coin variations. I understand how to tell the difference between them. What I'd really like to know is which variation came first. I'd also like to know why the dies were modified. Year: 1964 & 1964-D Type: Roosevelt Dime Diff: Pointed Tail & Straight Tail Year: 1928S Type: Lincoln Cent Diff: Small Mintmark & Large Mintmark Year: 1960 & 1960-D Type: Lincoln Cent Diff: Small Date & Large Date Year: 1970-S Type: Lincoln Cent Diff: Small Date & Large Date
As to Lincoln Cents ask the expert. coppercoins.com The guy on that web site has 2 books out on just that coin. Also, he has taken close to 10,000 photos of just that coin. If you can't get an answer from him then it just can't be answered.
The answers are rather simple - the '28-S, they used two different mint mark punches - they are not all identical. As for the large and small date coins, the dies were made from different hubs and there was a difference in the size and shape in the numerals of each. There was no conscious effort to make them different - it just turned out that way.
This website says the 1964 pointed tail came first. The straight tail variety was the result of a new obverse hub. http://www.richardsrooseveltreview.com/1964.htm According to this website, the 1960 small date came first. The master dies were remade because of die breaks and filled dies. http://www.scvhistory.com/scvhistory/signal/coins/sg070205-coins.htm According to the Red Book, the small mintmark was used on all minor coins starting in 1909. Variations in the size occurred through 1945, with notable differences in 1928, hence the small and large mintmark varieties. It sounds to me that in 1928, the small mintmark variety was produced before the large mintmark variety. I'm not positive, though. I haven't been able to find any answers for the 1970 small date/large date varieties.
According to this website, the 1970 small date generally has a weakly struck LIBERTY, while the large date generally has a strongly struck LIBERTY. The small date is more scarce. I'm going to guess that the mint changed the die to the large date because they caught on to their weak strike problem in the small dates. I'm not positive, though. http://koinpro.tripod.com/Articles/1970S1cSmAndLgDtCompare.htm
The 1970 small/large date cents are quite a bit harder to tell apart then their 1960 cousins. I believe the reason for the change to a larger zero in the date had to do with the fact that a smaller zero will have a smaller and therefor easier to break or damage central raised area, the larger zero was probably introduced in an attempt to prolong die life.