Whats this?

the house has radiant baseboard heat,

my question is, what is that valve/release looking thing in the center of the pic?

Bad attachment Joseph. Try again

my bad, there it is.

33W295_Shagbark Ln 163.JPG

It may be an air seperator.
Looks older than the ones I’m used to.

An air separator ?
is it sort of like a presure balancing device?

It removes air in the system that happens when water is added with disoved air.

FOUND it

Oh,I see !! its like a bleed valves on radiators, only this one handles the whole shebang at once. Very cool

thanks !

Never seen one like that Michael. Nice find.