Is There A Custom Of Adding An Unnecessary 1 Cent Stamp?

Hi all – In looking at some covers from the 1970s and 1980s, I keep seeing an additional and unnecessary 1 cent stamp thrown onto the letter.

Examples below. These covers have the full first ounce stamp, plus the 1 cent stamp, which is always in the bottom left for some reason...




Note that the covers on that website (PostalHistory.com) for Arizona during this period are dominated by the two recipients above. It looks like the recipient affixed the stamps, not the sender, because there are tons of covers for those two recipients, all with the same placement pattern and with a rubber-stamped recipient name and address. All these senders couldn't have had rubber stamps made for specific recipients. I assume these were SASE envelopes for some business purpose. I'm not sure how being SASE would have influenced the inclusion of the extra cent of postage though.

What do you think was going on here? An extra cent doesn't buy you anything as far extra ounces or services during those decades.

Thanks.

I found this in Arthur Rupert's obituary:

The mailers were Rupert and Lund. Purely philatelic.
Up to this era (before it got too costly for most) it was common to collect postmarks from every town in a certain state or states. Collectors like Rupert and Lund would send envelopes under cover to the various postmasters. The inner envelopes would be addressed back to themselves. The extra stamp is hoping to get an example of any second postmark device (like a round dater), but both of these failed in that sense. The one sent back/forth at Tortilla Flat at least got the postmaster to sign it and add her box cancel effectively as a return address.

Add: Here is a group of about 250 covers from Arizona post offices (most of them!) in 1974. In this case, I know there were at least three collectors in the same area doing the same thing. They would get together and combine their three return envelopes in the same mailing to each postmaster. This cut down their expenses quite a bit. The covers for Chandler Heights and Tortilla Flats are at the bottom of the center and right columns.