I had never even heard of benchmarking until I first visited Geocaching.com. I find the idea really appealing, in fact I can think of a couple of markers to go visit already! I remember seeing one alongside Front Street in Tyler where I live. It was a brass disk set into the concrete next to the sidewalk. It caught my attention, so I took a look at it. I knew what it was but couldn't decipher the numbers on it. Fortunately I remember exactly where it is. I also remember seeing a concrete post with a disk on it at Tyler State Park many years ago, but I don't know if it was a USGS marker or not (I guess there's only one way to find out)!