✅ SOLVED Brass tack? (Solution: Saw bolt or rivet)

[robertk]

I realize this is probably just some generic piece of hardware, but I'm hoping someone might know more about exactly what it is or what it was used for. Found at a late 1800's home site. It's shaped like a tack or possibly a cufflink -- a half inch flat disc with beveled edge and a square post in the back. It's probably copper or brass, feels solid and heavy, does not stick to a magnet (it had a TID of 84 on the Deus II, and a slight red patina, which is common for copper and brass here). The square shank seems complete but I can't be sure. And I can't make out any writing or pattern or anything on either side of it. It seems too short to be useful as a fastener, and being made of copper or brass seems odd for a fastener as well. Does anyone know what it really is?

Front, side, and back.

 

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[pepperj]

If I had dug it I would of thought some sort of a saw nut.

 

[Tony in SC]

Looks like a countersunk rivet? Pepper could be right?

 

[robertk]

I looked up antique saw hardware and I see a bunch of things that do look very similar, and brass seems to be a popular material. Some of them look just like this one except where the square part ends, there would be a round threaded part. I can't tell if this one is broken at that point or not, but I'm thinking it probably is, and the threaded part just got broken off. So I think @pepperj nailed it. (So to speak, since it would have been a screw.). I'm calling it solved. Thanks!

 

[bowwinkles]

100x Antique Brass Double Headed Rivets 6/8/10 Mm Leather Rivets Studs ..​

 

[bowwinkles]

I remember using these also:

vintage copper leather rivits at DuckDuckGo

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[robertk]

I remember using these also:

vintage copper leather rivits at DuckDuckGo

DuckDuckGo. Privacy, Simplified.

duckduckgo.com

That led me to some searches for antique rivets, and there are some that seem really close. Except I couldn't see any with a square pin -- all the examples I saw were round. But aside from that, this definitely seems to fit "countersunk rivet".