How @ a good back photo? might help ID'ing easier. I think it's to large for a jeans button though it might be an end cap for an atlas weight lifting bar.
I'll throw a guess of 70's , but it is a pure guess.
I believe the '70's was the time of the first gas shortage threats,
and although gas theft probably started with the invention of gas,
concentrated fear of gas theft probably started with the shortage.