It is about the size of a twelve guage shotgun shell in diameter. That's what I thought it was at first but it is just a disc and it says U.S.G.S. B.M. Any Ideas?
I found it in Dialville, Texas at a home that is 103 years old. The house is next to where a railroad ran through. The rail road is not used anymore, in fact the rails and ties are gone now.
While it may seem like it is not used anymore that may not have been the case, there are two type of USGS benchmark markers; vertical markers have elevation data stamped on them and horizontal markers are just plain discs. What you have is a benchmark marker used for horizontal surveys etc.
I would recommend anytime anyone finds a displaced benchmark that you contact the National Geodetic Survey advisor in your state to report it (in the event that they need to have a replacement marker mounted).