Frame size on Ruger single action question

It seems like I have read here that all single action rugers were on same frame. If so, how come some are flat top and some have the ears around the rear sight? Also the 2 or 3 digit prefix in serial. What am I not understanding? Thanks. Triker

There are at least 3 SA frame sizes in current production:
-Single Six
-Blackhawk Flattop/New Vaquero
-Regular Blackhawk (and possibly some Vaqueros, such as .44M)

Considering the New Model Single Actions and cylinder frames:

From 1972-73 forward the .357/.41Mag/.44Mag/.45 Colt were ALL on the large frame. The .44Mag is ALWAYS on the large frame (flattop, regular, Vaquero / Old Model or New Model) regardless of what you hear. The original Vaqueros were all on the same large frame. Then along came the New Vaquero and the flattops which are all on the medium frame. So that covers 'most' of the New Model frame variations.

Cylinder frames that I am aware of:

Bearcat frame (smallest) -- (.22)

Single Six/Baby Vaquero frame (small) -- (.22 and .32s)

Flattop BH/New Vaquero (medium) -- (9mm/.357/.44 Special/.45ACP/.45 Colt)

BHs and SBHs with ears, .44Mag flattop, and original Vaqueros (large) -- (.30/9mm/.357/.41Mag/.44Mag/.45ACP/.45 Colt)

There is one more frame variation, the .357 Max which I believe is an extended large frame.

Maybe others, but these are the ones I am familiar with.

When comparing serial #s, the medium frames seem to be stamped with 3 digits prefixs.

All Ruger single actions - except the Bearcat - use the same GRIP FRAME footprint. The CYLINDER FRAMES vary in 3 sizes, Single Six, Flattop/New Vaquero, and old Vaquero/Blackhawk/Super Blackhawk, small, mid, and large. But all 3 sizes share the same grip frame footprints. There's the confusion.