At the same time the 2 inch square butts were available, there were also a batch of 3 inch heavy barrel square butt Model 60's for sale. They were advertised together in ShotGun News by a distributor for who they were made.
I bought one of the 3 inchers; still have it. I bought it in October, 1984 and my dealer had to order it from the distributor for me. S/N is AEV65XX range. These aren't mentioned in SCS&W III, either. I wanted a 2 incher square butt to go with it but couldn't afford both.
My notes from the time of purchase say that my 3 incher was one of 5,000 made for John Jovino Inc. My guess is that the 2 inch guns were a similar deal for the same distributor.