That is a very nice suspender buckle! I've seen that one before and it was described as a "Civil War" suspender buckle found in a camp. TheCannonballGuy is right. It is not the same style as the one shown in his picture. The style in his picture comes in a huge variety and all have a patent date on them. Usually there is also 3 numbers. For example... PAT 420 1871. The 420 could be April 20, but I think it is the size or possibly the style. The numbers change frequently. Plus I have one that reads 432...that can't be April 32, lol. The one you posted doesn't have a patent date. Those type usually never does until you get into the 70's. For the most part, if it is from the 70's, it will say so. I believe you are correct with your time period. Nice find!