Wow Gary thats very cool, love the simplicity. I'll take a crack at the mods. Don't laugh if I 'blow it'.
1- Checkered front strap.
2- S&W adjustable revolver sights - very popular mod 'back then'.
3- Over size slide stop shaft - 2 piece. Paul Liebenberg still uses a similar mod on his pistols, he used to work for Frank Pachmayr.
4- Trigger job
5- 'Extended' guide rod (Not modern day 'full length')
6- Over size firing pin stop?? *shrugs*
7- Extended shelf on the slide safety
Wonderful piece of history!!