Now that I suckered you in....I may have lied about the prize. Other than the satisfaction of knowing you're a pool part pro and helped a friend of a goofy guy on the forum there is no prize.
Without further lies, here's the part...I believe it is a in floor cleaning device from many moons ago. This is the only one in the pool, there is a ball valve that operates it and only it.
If you turn it on now, it apparently rises from the bottom and sprays water everywhere. (If it'll help I'm willing to waste my friends water just so I can see this and take a pic of it).
If this is the wrong forum for this, I'm sorry...I took a wild guess as to the appropriate forum.