This Staff Officer Button has a backmark of P "something" & Johnson. I was wondering if this was made pre civil war or maybe specially made in Savannah (where I dug it)?
Your button's backmark says Steele & Johnson &. (Note the e on the end of Steele, and the two &-marks.) The button backmark-dating book by McGuinn-&-Bazelon shows a photo of it, and says it dates from 1857 to 1865. That company was one of the four main (most productive) button-manufacturers in the US during the 1800s. Got to be careful about dating Steele & Johnson backmarks, because the company lasted until 1920.