How do you determine the difference between type I and II SBA 1981 proofs.

Isaac S. writes: How do you determine the difference between type I and II SBA 1981 proofs.
 
Ah, this is the “broken punch” story. All the dies are made in Philadelphia and so were the mint mark punches. Mint Workers punched in the mint mark by hand just before the dies were put into service. About three quarters through the run of 1979 Proof Sets, the mint mark punch that had been in service for many years, broke. If you look at the coins made from dies using this punch, the mint mark appears as more of a blob than a letter “s”. In the haste to make a new punch and get the proof sets production going again, they sent a punch that probably wasn’t annealed properly. The rest of the run of 1979 proof sets have a distinct “S” but the ends of the “S” touch and the holes are very small. These are respectively 1979 Type I and 1979 Type II proofs. These mint marks appear on the other proof coins as well.

In 1981, the poorly annealed punch was still in use, but again broke giving rise to yet another mint mark variety. The type 1981 type I is the same as the 1979 Type II. The ends of the “S” on the 1981 Type II has separation from the body of the “S” There is a lot more space in the holes of the “S” and the holes are more “U” shaped than round.