The brass ones you mention, if about two and a half inches in diameter, are typically benchmarks. USGS and other government agencies set them, quite often in stone or in concrete posts, in the course of various types of surveys. The pictured concrete item might be a type of survey hub too, but it's not one that I am familiar with.I once saw something similar embedded in a very old concrete road as a cross-walk marker. Normally when I find these, they're brass markers denoting who/what/when.
Are you certain it is made of concrete? Could it be corroded zinc or pot metal?Can any one identify this? I found it in my back yard.
6" diameter under mushroom capAre you certain it is made of concrete? Could it be corroded zinc or pot metal?
Please measure (not metric) diameter of the small end. The diameter of that shank directly under the flared cap portion would be helpful too if you have a set of calipers. I think I know what it might be if it is made of metal and not concrete. If it what I suspect, corrosion from burial gave it that pockmarked appearance.