Roper Whitney No 20 versus No 20-1
 

Hi Punchers,
I am faced with a choice between a used Roper Whitney "No. 20" and a
"No. 20-1" punch, but I am not aware of the difference between the
two, and I am not in a position to physically compare them. Can
anybody help? From Roper's current catalog I see they have a No 20 and
a No 20 CTL, but no mention of this other variant called 20-1.
Any advice?
Many thanks!
-Ram