A little background. I invited several metal detectorists to explore area around my colonial house. So far, except for a few wheat pennies, they have found about 30 pounds of iron. Largely farming relics. About 6" down, they found this. It may be important to note the house has never had steam heat. The shape immediately suggests to me some connection with the thermostat in an auto's cooling system. I think it important to note that it has a "bleed" allowing fluid to flow out of it, perhaps to a pressure or temperature gauge. It has a part number, but it is now illegible. Anyone recognize it?

I bead blasted it, and have tried to attach a few pictures (I hope that worked)

What I am calling a "bleed" is shown in the second picture, just below the tubular portion. It could be mistaken for a shadow.

Automatic choke heat tube source? Does the end of the tube opposite the threaded fitting have a small opening?

No, only what I am calling a "bleed" into the main fitting itself. That is shown in the second picture, although it might look like a shadow. So, the brass fitting can draw fluid or pressure from the main fitting. I was assuming it was part of the cooling system, although I suppose it could mount on an exhaust flange.

A friend just suggested it could have been mounted under a single barrel carb to pull a vacuum for something. Makes sense.

Wild azz guess.....

Any history of any steam powered machinery or equipment in your local area?

Looks like it could have been a flange that was installed in a steam line so that a pressure gauge could be installed.....

^ this

Old School approach for a manifold vacuum source.

Modern interpretation:

I wondered about that possibility. While it became a manufacturing town, my property was a large farm. That is why I mentioned the house had never had steam heat (or any heat, until my parents bought it).

Probably an old tractor part.

It could also introduce heat to the carb, I suppose, but more likely pulls manifold vacuum.