I've done some research but haven't been able to date this pin. Back reads m.s. Meyer New York. The remains of the screw attachment seem to me hand made much like early drawer hardware I've found. Yes I know it was mangled by the cleaning but it was found in an iron strap sandwich and wasn't identifiable.
It is definitely a US Army 2nd Infantry Regiment "distinctive unit insignia." The screw-pin attachment on the back of yours dates it from the 1890s through the 1930s. Army Noli Me Tangere Second Infantry Regiment Crest
When I first answered your post, I did not have the time needed to do additional research on your "distinctive unit insignia" badge's unit, the US Army 2nd Infantry Regiment. Having done so, I can narrow down your badge's date-range significantly. The current version of the unit's emblem, which you have, was adopted in 1936.
I did additional research because I thought you'd like to know about the history of the distinctive unit insignia badge you found. The 2nd Infantry Regiment was part of General George S. Patton's US 3rd Army, and it participated in the Battle of The Bulge. In the latter 1960s it was heavily involved in Vietnam combat. http://en.wikipedia.org/wiki/2nd_Infantry_Regiment_(United_States)
