Who originated the 3 3/8" x 2 1/8" size for credit and related cards?
I know there is an international standard for it, but that was probably based on some existing defacto standard.
Charge mechanisms go way back (1920’s or earlier) with the first credit card as we know it today being the Diner’s Club card in about 1950. But their first cards were cardboard and I’m not finding what the size was.
So, who came up with it?
The first mass-market, general-purchase card was BankAmeriCard, issued by BofA around 1960, which morphed into Visa when it became a multi-bank card. I seem to recall the original card being a little larger than the current size - maybe taller?
I can’t think of a single reason for the EXACT size, but four or five things come to mind about the approximate size. It’s probably the same size as most mass-issued membership cards, and I’d bet that most states’s driver’s licenses of the time are within a hair of that size as well. The fundamental reason for the size is that it would fit conveniently in an half-fold wallet, which would have its size set (more or less) by the size of bills.
The current size is within a bit of standard business card size and I seem to remember Amex cards originally being exactly that size as well - so again we have a size that would have been of a convenient scale to carry with folded cash, possibly going back to the 1930s or earlier. (Not sure when the current size of business card came into use.)
It would be interesting to look at old catalogs etc. and see when wallets first developed the rows of card holders - was it earlier, for membership cards, store cards and the like, or not until sometime around the early 1960s when credit/charge cards started becoming a common personal item?
The standard size for department-store cards was, I’m sure, quite a bit narrower, but about the same length. That seemed to be set by the convenient size of what were called “zipzaps” - the imprinting devices that were manually operated, either with a lever handle or by a head that was slid back and forth over the charge slips. Since those were handwritten, there was a substantial clerical staff needed to enter them into the system - at least the trusty IBM 360 computer was around by then to take care of the rest.
A little chicken and egg, but it does raise the question of whether Addressograph plates had anything to do with it, along these lines.
For the set here who think video games were invented long ago, Addressograph was a system for repeated addressing envelopes in the pre-printer days. It used embossed aluminum plates and a “zipzap” - never heard that term, but a good word - to print the address in purple ink by pressing through the envelope to the embossed plate and hitting the high points with an ink roller. Hadn’t thought about them for years, but adapting the recording tech to credit cards might have had an influence on the card size. (I still remember getting envelopes addressed that way - they had a peculiar feel from the plate embossing through both sides of the paper.) (No, I’m not THAT old but a few old-guard companies used them well into the 1970s.)
It occurs to me that the post-Pong generation might not know what a mechanical card recorder looks like, either. They were most common at gas stations - and there’s another place that might have had a lot to do with setting the card size and form.
CMC
Perhaps it found its current size by conforming to the standard business card size (3.5" x 2"), so that it fits easily in most wallets or plastic holders. As to why business cards are that size is another question.
As a point of reference, US currency went to the current size of approx. 6 x 2.5 in 1929. It had previously been 7.5 x 3. Diner’s Club didn’t come along until 1950, but the standard would have been set in 1930 at the earliest.
It may all be that it’s just a convenient and durable size for its purpose - so many small personal cards are within a few percent of that size that it seems to be a natural “harmonic point” between useful information area and easy carrying/handling. Any squarer, or any narrower, and it would be more prone to bending damage. Ditto for any size much larger. Any smaller, and it would be easier to lose and information (such as on a driver’s license) would be too cramped. In other words, maybe this size just “is” because it is.
Interesting question. I have a very strong memory of my parents having different sized cards, probably early 70’s. I think it was probably pretty standardized by then, but they had at least one card that was narrower, I want to say grey or silver. Perhaps an american express or sears?
Memory is a funny thing.
Why would they need to send multiple envelopes to the same address?
I don’t have an answer to who originally chose the size, but there is a Wikipedia article on the standard for credit card sizes – ISO/IEC 7810 – which describes the size as ID-1, and gives it as 85.60 × 53.98 mm. That number of significant digits suggests that the size was originally given in inches and so probably originated in the United States.
you would mass mail bills, newspapers, magazines to your customers. each address plate was a different address.
I just compared a business card I believe to be standard size, obtained in the last few months, with a credit-card-sized card used for the laundry facilities in my apartment building. The business card is about 1/8" shorter in the vertical (short) dimension and about 1/8" longer in the horizontal (long) dimension.
I suppose 1/8" is close enough for wallet slots, etc. 
Business Card 3.5" x 2"
Credit Card : 3.375" x 2.125"
If I wanted commonality with business cards I think I’d make both dimensions either the same or smaller than a business card, so it could fit in all the same places.
Just a guess…
I 4ever my parents Sears card from the late’70s thru the mid '80s being about half the height as their other credit cards. I always thought that was somewhat strange.
I seem to recall Roman chariot drivers had pockets in their dress armour of credit card size and it all followed from that.
Zip, Zap, National Bank Visa - An ad from 1970s New Zealand.
I think it all relates to the practical width of the machines that cut the paper, steel, cloth, plastic, etc…with minimal loss of material.
I’m gonna guess 48" x 10’ was pretty standard’ish.
How large is a usable cow hide 36sq ft? Wallets stuffed in the larger bills until the smaller versions came along.
Plastics came later but the rest was already established, so therefore it followed.