🔎 UNIDENTIFIED Concave Button - Looking for approximate date

[Iron Buzz]

I found this yesterday at a site that dates to 1855. It is the only possibly period artifact I found there so I'd love to be able to say conclusively how old it is. I have had one exert state 1820s but he provided no proof beyond his (rather formidable) reputation. There is no design on the front, and the only possibly identifiable mark is a circle of triangles around the loop shank on the back.

Please refrain from guessing. Do you know that backmark or have a photo of something similar?

 

[Older The Better]

I can do similar, my site I’ve got near 1830, not concave but it has a triangle pattern around the shank. Nothing on the front, strongly suspect it’s from a na trade site.

 

[CRUSADER]

1790-1830