Now I wonder if these were ever really used as actual postage stamps? Besides the size and weight, stamps need to be "cancelled" by, well, stamping them with an

Now I wonder if these were ever really used as actual postage stamps? Besides the size and weight, stamps need to be "cancelled" by, well, stamping them with another kind of stamp (https://en.wikipedia.org/wiki/Cancellation_(mail) https://en.wikipedia.org/wiki/Cancellation_(mail)) before an envelope goes in the mail, and I can't imagine how that would work with these... EDIT: there are also first day covers using these stamps available (https://boingboing.net/2022/07/07/look-at-these-cool-1970s-postage-stamps-from-bhutan-which-are-tiny-vinyl-phonograph-records.html https://boingboing.net/2022/07/07/look-at-these-cool-1970s-p...), and the photo shows that it actually works, but not really well, especially with the black one...