I am completely ignorant on bench marking but I took pictures of two that I've stumbled upon and thought folks in this forum might be interested in.
The first one is outside of Superior, Arizona along a road that parallels US 60.
The second is along the Denali Highway in Alaska and is not listed in the NGS Datasheet marker database.
I hope these are useful in some way!
Bonnie (Gal in AZ)