That’s why I asked if it was a post card. I haven’t gotten into ‘postal history’ much(yet). But I know 1ct was the postcard rate for a long time. Not sure how it was enough to mail this…
Maybe there were special rates for small envelopes? Sidetrack: I remember not too too long ago the Post Office said they would n't guarentee delivery of small envelopes anymore.
I found a couple websites with post card rate history but its a bit confusing. Post card rate was 1 cent from 1898 until Nov 1917.
Then again from 1919 until 1952, except maybe 1925 to 28.
The return address is Stanley Rule and Level Company. They joined with Stanley Works, manufacturer of hardware in 1920, operating as two divisions of one company.
I'm leaning toward the possibility these spurs were mailed 1916-1917 or early 1920s.