Found AT site occupied mid 1800s thru mid 1900s
first thought civilian but after cleaning now thinkmaybe a military. button is 23mm diameter
anyone know? thanks
In button-collector lingo, your button is a Civilian-usage "false 3-piece" imitation of an actual 1832-to-1902 US Army Staff Officer button. It is called a "false 3-piece" because it is a 2-piece button manufactured to resemble a 3-piece button (which is more expensive to make). Yours appears to have an iron back, which is partially rusted out. There were no actual US Military-issue ironbacked false 3-piece buttons.
When i was looking up information on the button I had I saw similar ones to the one you have here. This is the site I went to William Leigh: Civil War Era Button Collectors. I believe it shold be under the US Central Government Buttons. Hope this helps ya some
CB Guy is 100% correct. Some NY governmentalservices used the same button construction for the NY Staff Officers button (false 3-piece) that date late 1800s to early 1900s.