“A three-legged stool with a very narrow back, does it serve a specific purpose?”
Answer: “Milking stool.”
it's definitely an egg separator. You crack the egg into the cup, pour the white out and the yolk remains in the cup.
This one not but wouldn't be too sure about that glass plug ????
It's the location of the manholes/wells/valves.
the center of the T-shaped groove represents your location, so for the top sign, there's a valve 0.8 meters left, and 11.2 meters behind you.
It´s a Sanistand type female urinal.