Just occurs to me there is a label that is NOT visible in any of the scenes.
If we in the theater had a rock that had to go back in the right place on stage every night, there wouldn't be a label on the rock or anywhere else to make sure you got the right one. That's what Stage Manager's diagrams (and crew memory) is for. After all, the cast can remember two hours of blocking and choreography -- the crew can certainly remember that the slightly brownish rock is the one on the left, and the l-shaped rock is near the leg.
No, what is marked in these cases is the FLOOR. Spiked (behind the prop, so the audience shouldn't see them when the item is in place) so you can get it to the exact geometric relationship each time.
I haven't seen anything like all those little bits of colored tape in any of the Apollo Surface Record.
(At least the astronauts wouldn't need glow tape -- they aren't required to find their way on set in the dark!)