Wow! Is that socket on the left really from 1949? I thought the intermediate serif logo ended in 1941. Could it be that the date stamp is actually 1936 or 1939? Or maybe when they phased out the italic style in 1949, someone made a mistake and used a 1941 type logo stamp?( There was a short-lived intermediate style after the 47-49 italic style and before the new SW-xx1 style in 1950).
Anyway, here's what I've found up to now:
So far, from my looking at numerous pictures of sockets with date stamps is that the type which started in 1936 went to early 1941. On these, the "Snap-On" logo has curly intermediate serifs with the lower serif of the "p" segueing into the underline. And the knurling was bordered on both the top and bottom with a ring.
1940:
The ones from late 1941 have a new "Snap-On" logo without serifs. The underline is broken to clear the "p" There is still the double ring bordering the knurling.
1941:
The lower ring bordering the knurling disappears sometime after 1942. I haven't pinpointed it yet because I still haven't seen any 1943 sockets and the E stamped sockets usually don't have the lower ring. But I actually suspect that the single or double ring bordering the knurling may not have been standardized because I have seen a mix of single or double rings in 1944 and 45.
1944-E:
But this 1945-G has the lower ring!:
Generally, this one ring and sans-serif style continues through to early 1947.
Late 1947:
The italic logo style appears sometime in 1947. I am not sure when the italic style was phased out but I have a picture of an early 1950 socket and the logo is back to the non-italic.
Early 1950 SW-320-1/2:
The old knurled SW xx0 sockets are replaced by the new, non-knurled, SW xx1 series in early 1950.
