Within a few miles I found all these examples of Pacific Crest Trail markers. The first is the earliest where someone (typically a Boy Scout) would mark the bark of the tree with a hatchet. In this case the double vertical rectangle where the lower rectangle is bigger (like an upside-down exclamation point) is for the PCT. Next two are early PCT diamond markers (one painted and one embossed). Then there are wood ones with the PCT pattern pressed into it. I’ve also seen trail posts like this. Then there is the modern trail marker. Finally in many spots there are just diamonds which are just painted white.