I have no ideas what these things are for other then they belonged to the usps when they were U.S. Mail. I have 31 of the things I got mixed in a lot ages ago on ebay. I think they are copper. They are thin too 10 stacked is about a half inch tall.
A: My father was in the postal service for 25 years. He had one of these lapel pins. Looks like you got a set without the two pins that were superglued to the back.
And I had a steam engine, that was running on Esbit too