Yeah Mike what kinda kook collects Model 59 varients...Hey....wait a minute!
There are actually quite a few changes just within the Model 59 especially in the early years if you look at them closely,
The earliest version had smooth tangs and are very collectable.
saw one for sale over 10 years ago and backed out of the bidding well above $1k.
Another very unique feature of early production guns was the changes in frame relief cuts to clear the safety lever, initially both sides were relieved , (the right side was probably done in anticipation of a future ambi safety lever is my guess) at some point they changed the safety lever spacing making it stick out further to clear the 59's frame and the relief cuts ceased.
Lots of little things depending on how fine you set the microscope.
Barrel bushings, slide stop cuts, mag release buttons, magazine followers etc.
Great guns in their day, it's too bad they didn't put more attention into the grip frame contours and offer nicer stocks or they would be much more collectable.
They are kinda ugly and feel like a brick but it was my first 9mm and has a special place in my heart.