Interesting article, but it contains a number of inaccurate statements. The rifle was initially introduced as the Stevens Model 325 - not the 330 - in 30-30 only. Had one that was virtually new. For some reason or other, I never got around to shooting it. The 250-3000 chambering is a new one on me, and I doubt if Savage even considered it. (I had a 340V in 225 Winchester, a rifle I never felt comfortable with as I thought that the factory cartridge was pushing the limits of the action. I shot it with less than maximum handloads.) Early rifles had a pivoting ejector, superior to the plunger ejector mentioned. The 340B 222 I now have (manufactured in 1953 - Savage jumped on the 222 band wagon quite early) has this ejector and dual extractors. There are so many variations in certain design features - mostly cost-savings measures - that it's difficult to keep track of them.
All in all, this entire series of rifles is, in my estimation, largely overlooked and are sleepers. There's a dizzying list of house branded 340's in addtion to the Stevens/Savage variations. Some day collectors will be paying big bucks to get one of each (providing, of course, that
gun collecting is still legal then...)

(By the way, I think a scoped 340 in 30-30 can do better than "sub-2 inch" groups at 75 yards!)

Also, prior to 1968 this entire series was not serial numbered. Pre '68 guns have a barrel code indicating the year of manufacture.

Can't help with serial numbered guns; not sure if any records exist for the 340