[Stevens was gone by 1950.]
Don't be so sure. Savage's owned the Stevens name since 1920, and they still occasionally put it on something, when it behooves them. As witness the very recent Stevens Model 200 C.F. econo-boltgun.
So, really, "Stevens Arms" has been "gone" for 87 years - yet here we have all these pesky two year old and fifty year old Stevens rifles & shotguns.
1939 is argueably (some experts say 1938) the first year of Stevens 22/410 production, and I haven't ever seen one made prior to GCA-68 with a serial number - just assembly numbers, which are often mistaken for serial numbers.