Know what this is?

This photo was taken looking up between joists of main floor. The black metal item appears to extend to the exterior (although I could not confirm that due to new construction). I don’t know if it belongs in this forum or not.




By chance is this shroud looking part “vented” to the outside? Is it located under the Kitchen area, say under the cooktop or range, either in line with the cabinetry or under an island? Offhand it looks like a sidewall direct vent for some kind of downdraft exhaust system.
Picture isn’t real clear, nothing to compare too, or help with dimensional comparison, but it does resemble what I’ve seen.

Looks like the end of an old expansion tank.

Home made combustion air opening?

I think Greg might have it. It is about the right size and location. And the shape does imply a fan housing, with the inlet at the top. The stove is currently at an interior wall, and there is original galvanized ducting in the attic above the stove but who knows what might have been at one time. No doubt an exhaust from the floor above. Thanks.