How to date these when there are no date codes on them. Below are four 5/8 inch X-20 wrenches, they are all 1920's. Bottom wrench is a Blue Points X-20. (not in the cats) its hard to date blue points, but I would guess its mid 20s, these are very hard to find. Next up, probaby the first bp wrench type, its short about 9 inches, has a very deep offset, no date code, so I would date it 26-27. Next up, date code 6-28. length 9-3/4. shank diam. 19/32. Next up date code -29, length 10 inches, shank diam 1/2. The mid 20s x series have a distinct offset which is much larger than post 1927, they are shorter. I have not seen an x series with a 27 date code. The 28-29 x series are somewhat longer and have a date code with 28-29. the x-30 appears first in the 1928 cat.. In general, the lengths get longer thru the mid 30s and after 1933 they stay the same. But exact lengths are often somewhat different than whats listed in the cats.
1930s: Some of the early 30s have date codes, but in about 1930 most of the wrenches were stamped (pat no 1424069) or (pat no 1424069-1). In about 1937-38 (made in USA) stamp was added.
So, 20s, no pat no, no made in usa. Early 30s pat. no, but no USA, late 30s and early 40s, would have made in USA.
