During World War II, there was a mad rush to produce weapons for the war, and we had all sorts of companies that had previously had nothing to do with firearms re-tooling their factories to produce rifles for the military. Some M1 Carbines were made by the “National Postal Meter” company. (Some were also made by IBM.) But what on earth is a “postal meter?”
A scale for weighing pieces of mail.
ETA: At that time I believe all such scales would have been using springs for measuring the weights. Since the most difficult part AIUI for manufacturing modern firearms are the various spring mechanisms it makes a certain amount of sense to take a manufacturer that is already used to working with springs and then teach them the rest of what they need to make firearms.
You ever get mail with a printed stamp of sorts on the envelope?
Those are printed by a postal meter. Most large companies have them because it saves them having to have millions of stamps on stock.
The days mailings are fed through the machine, the postal rate set by means of a dial.
The machine is “filled” by someone going to the post office with a swipe card and the cash/cheque for the amount of money they want the machine filled with.
Ex postie here
This is completely ignoring the fact that the question is about the term around the time of World War II.
OtakuLoki gave the relevant description.
There aren’t that many springs in most WWII firearms and they’re not that hard to make, AFAIK. The problem was getting the tolerances and interchangeabilities right, so that the parts for a Lee-Enfield No. 4 Mk I made by Savage-Stevens Arms would interchange with a Lee-Enfield No. 4 Mk I made by BSA.
This was a problem for the Howard Auto Cultivator Company, who made around 350 Enfield No. 2 Mk I revolvers during WWII- the parts from the guns wouldn’t interchange with Enfield revolvers made by anyone else, or even with other Enfield revolvers made by HAC. The HAC revolvers are now worth quite a bit of money, oddly enough.
It’s quite interesting to see what sort of companies found themselves making gun parts during WWII- various Fountain Pen companies in the UK made charger clips for Lee-Enfield rifles, the National Postal Meter company were making M1 carbines in the US, and a Service Station workshop in New Zealand and a Vacuum-Cleaner company in Australia were making machine-guns…
Not so fast.
OtakuLoki may have given the relevant description for the US, but that’s not where Chowder is, and even in the US I’m not so sure.
I’ll give you the three basic types of mail (by postage method) as they exist in Australia, and as they exist also in the rest of the world (including the United States), but no doubt by other names:
- Stamped mail. This is self explanatory. This is for low volume or occasional mailers (such as individuals).
- “Imprint” or “Full Rate” mail. This is the stuff that simply has a pre-printed design in place of a stamp, that says something like “POSTAGE PAID NEW YORK”. This is for the high volume mailers like the electric company or American Express. Those guys lodge mail in terms of tons, literally.
3. (bolded for relevance) “Franked Mail”. This is for smaller companies that don’t mail enough stuff to warrant backing a semi truck up to the loading dock of a major national sorting centre, but who post more than your Aunty Jean’s Xmas cards. Outfits like regional clubs that send out newsletters etc are fond of these. Postage involves using a machine called a franking machine or a POSTAGE METER to run off a few hundred or thousand articles. You’ll actually often see the word “meter” appear on the resulting franking impression. The unit is tamper-sealed a bit like the electricity meter on your house. They were around in WWII.
The item you refer to is known in postal circles by its technical name of a …erm… scale.
- TLD (twenty years in the postal industry)
And here in Canada, hundreds of thousands of Bren light machine guns were produced by Inglis, known before the war for their washing-machines; likewise, the Montreal Locomotive works turned out tanks, and the 40mm Bofors AA gun at the exit of the historic site I work at has a brass plate on the side proclaiming it to be the work of the Otis Elevator Company.
United States Postal Service page on postal meters
Edit: I googled “postal meter” and got a page full of hits for “postage meter”.
Yeah, I’m with TheLoadedDog here. There’s a brief description of how postage meters work on the Wikipedia page about them; they’re still around, though perhaps not as common as they once were. And they’ve been manufactured in the USA since 1920.
My mother volunteered in my church’s business office when I was a wee lad. I always remember being fascinated by their postage meter, and also being admonished not to touch it lest I use up all the “postage”.
No, the description that he gave was wrong. A postage meter is not a postage scale–not during World War II, nor today, nor in any country in the Western world.
It seems I was right after all 
::shrugs modestly::
I hate to say this, but I really think that chowder was more correct than I was.
My apologies for any confusion my answer created.
Why do you hate to say it?
Don’t you like me?
::sniff::