Lugz is asking: is it “USA” or “Made in USA” under “Bonney”? It looks like “Made in USA” to me, so maybe 1933.
The specialty wrenches are going to be problematic dating because they were made in smaller numbers, probably in clusters intended to be sold over time (years, even). Could be the forging dies were used lighter than other models. If the dies were updated, the date codes could be updated, too, but if the forging die was good, why change it?
As to number replacement, I think early single-offset double box-end wrenches did go through a short period of confusion, Zenel examples someimes but not always, showing a Z-prefix to the same model numbers for CV alloy equivalents. For some stretches, the same size/purpose wrench could be made of carbon, CV, Zenel, Bonaloy, or “other.” Bonney tried to distinguish the specific alloy in the model numbers, at least for general-purpise wrenches, as Lugz said, but this is not a reliable rule for periods of rapid innovation or for speciakty wrenches.
I think the alloy-restrictions in WWII made those distinctions seem fussy, and the number changes after the war seem to indicate an attempt ti “rationalize” and unify the numbering system. Subsequent management and ownership changes, along with brand-mixing with other purchase manufacturers re-confused it.
BTW, I like it. I don’t think I have one, but I’ll have to check to be sure.