Some info from my notes: (as you said, all info is approximate).
A. Angeles Souvenir—late 1962 to late 1967. Thin leather, BUCK on snap, no rivets, no model number.
B. Atcheson Leather—late 1967 to early 1969. Leather, BUCK on flap, plain blank snap, Model #, tooling lines and dimple rivet on belt loop.
C. Buck leather shop—started early 1969.
1) Leather, BUCK on snap & flap, tooling lines on belt loop. Used maybe 2 years?
2) Leather, BUCK on snap and flap, plain belt loop, model # on back.
This info should also be in the 110 sticky at the Forum top here.
My 68-69 sheath, by the way, does not fit in any of that info.