What are these made of?

[mark hendricks]

I found these at an oil facility. They are rivets, about 3/4 inch in diameter.

[Frosty]

Rivets are usually mild but there are specialty fasteners of all types. If you really want to know try sparking them.

Frosty

[mark hendricks]

I should have mentioned they may be from the late twenties or early thirties. I see them on older tanks.

[orgtwister]

like frosty said i would try a sparking test on them i have cut alot of old rivets off from that era and they were mild steel i did alot of scraping in the past and cut alot off with a air chisel

[John Martin]

Spark Test. , there's a detailed BP for spark testing as well.