there are three designs. 1930-1935 single long knurling with no incised line above or below the knurling.
1936-45 small knurling with incised lines above and below knurling. 1944-49+. small knurling with incised line above knurling.
There is a overlap in 44-45. where you can find both types. In 1940, made in usa shows up (its odd, most other tools start in the late 30s with usa). Also in the middle of 47, the way they are made changes, you can find both in 47. Here is a odd thing, I cannot find any 1943 sockets, so if you have one post a pic.
