Stop in for a cup of coffee

Mattax said
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.

Pushing that a little earlier.... an almost identical stamp was issued in early 1914. The only difference was the first one was on watermarked paper. So, no way to tell the difference when its on the envelope. Th first one is actually more likely as it was printed for about 2 years and the second one only about 6 months. There's always a chance a stamp could be used long after it was printed. But usually businesses used them fairly quick after purchase.
The increased mail cost in 1918 was related to WWI. Not sure if that was directly for postal cost, but they did start free soldier mail in the fall of 1917.