Monogram Button ID or age help

[Iron Buzz]

I know next to nothing about old buttons so I'm hoping somebody can at least give me some idea of the period of this, if not some help with the monogram on it. Found in a Minnesota farm field that shows homes on an 1880 map. High likelihood of Swedish immigrants. I'm particularly curious about that style of loop, which is something I've never encountered before. (that's just mud that you see around the base of the shank.)

 

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[Tpmetal]

I've found a lot of old buttons, never anything like that. It's gorgeous. Is it lead, brass, or silver or what?

 

[Iron Buzz]

That's a very good question. Doesn't feel like it is lead. Not sure what tombac looks like. This has the color of aged bronze or brass. Feels light, but it is thin, too, so there's that.

 

[Iron Buzz]

I found this guide online, but there's no way this found in Minnesota button could date to the 1700's... is there? We were settled in the mid 1800's. But the shank perfectly matches the shank in the first sketch, and not any of the others.