Hmm...I'm thinking that might be white PVC pipe. Take a knife and, WITHOUT CUTTING YOURSELF....(or someone else! ), cut a groove into the white coating. If it scratches easily and is bright white inside, it's PVC pipe. If it's hard like rock.....well, I dunno. That would tend to not make a sprinkler head pop out like it's supposed to.
EDIT: Actually, it "could" be concrete and still make sense. Might be from a bird bath or lawn ornament that has water flowing, or some type of flowing-water display piece that someone built. ...But I'm betting it's PVC.
I wish these views had been included the first goaround. Sad thing is, it feels like I should "know" what this is...but at the moment I'm drawing a blank.
Allison, what's it look like on the inside, past the threads? Can you post that pic please? Also, see if the metal is magnetic. Got an idea swirling around...gonna have to wait for it to settle a bit, though. All I'll say right now is, maybe it's just a tad hasty to rule out this as possibly being a sprinkler head - but even more, I'm thinking something like a valve that turns a sprinkler system on and off. Gotta do some research.
Were you able to confirm whether the outer material is cement or other?
....Need to find out what's on the other side of the hole in the first pic of the OP. Dang - I gotta feeling this is gonna keep me awake half the night!
Ok, here's this. Maybe with this I can at least get some sleep...even though I haven't found an exact match yet.
I'm thinking it's an old model of water main shutoff valve. Fount a similar valve (top only) and, it may have been left in the ground after demolition of an old building, or updating of on-base water lines.
It's not a pop-up sprinkler. Been trying to find a match for it, as it looks a LOT like some of the lawn sprinkler shut-off valves I've seen out there. Just haven't found an exact match - for either the valve or the tool.
My thinking is that there used to be a pipe attached to the threads on the underside, and inside that pipe was a rod or shaft that went down, inside the pipe, to where the actual shut-off valve was. This would be for areas of moderately cold winters, where it was not normally necessary to drain the sprinkler systems. Nowdays, it's a given - drain the system before winter, or else risk getting fired! ...Anyway, that's my thoughts. But gotta stop here, as I'm burning up too much of my data allowance looking at all these search engine pics.
That is 100% a sprinkler head. Looks like 3/4" npt or 1/2" npt pipe threads, hard to tell size in pictures. The white you see is not concrete it most likely is oxidation from corrosion. Maybe mad of pot metal.