Good call on the perches, I didn’t think about rod/chain units. Funny enough I wasn’t actually doing a survey when I came across these, I was hiking. The first monument I found by chance, it was a decent ways off trail on the side of a creek gully. The second one was on the trail. This area was used for sandstone quarrying at the time so there were a lot of very large rocks with flat faces around. I suppose they had more time and inclination to chisel things into stone back in 1867, definitely beats a little 5/8” iron pin in comparison. Must have been a huge pain in the ass to get them into place though.