In our area, many will be Dyno tape tags (you know, the blue, green, black plastic tap with letters/numbers punched out that turn white...). Some are copper/metal plates with the numbers stamped in them. More creative ways I've seen: zip-ties around a tree branch (3 zip-ties, then space, 5 zip-ties, then space, 2 zip-ties, then space to give numbers 352) and bolts in same fashion as zip ties (3 bolts - space, 5 bolts - space, etc...), a laminated leaf with coords printed within the leaf design hanging in a tree.
If you find a tags with just 2 three digit number, they they are to replace the decimal of the N/W (ex: N45 23.456 W075 43.567 with tags reading 345 678, then new coords would be N45 23.345 W075 43.678).
Look on tree branches, under/behind signs, on fence postes, under beams, etc... keep looking, it's there!
Good luck!