two pipe steam system 1919 no radiator valves nor air vents see pics attached. need details

I see no pictures of a radiator... however, I do see one trap which is very likely a crossover trap.

Therefore... jumping wildly off the deep end here, I'm going to say that this is -- or was -- a vapour system, and there are flow control devices -- orifices or widgets -- in either the inlets or the outlets to the radiators. There has to be an air vent somewhere, but it will be on a dry return or where the dry returns join before dropping.

Any low level returns (below the boiler water line)?

But. We need pictures of a typical radiator, both inlet and outlet, and pictures farther back from the boiler, from enough to angles to sort out what is going where.

mattmia2 said:

I think that is a probably way too small air vent in the second picture(and probably unnecessary if the steam traps are working), but we have not seen a boiler or a radiator yet.

You are referring to that widget at the end of the horizontal pipe, @mattmia2 ? Indeed, if that's a vent it is way too small I wasn't just sure what it was -- thinking it might be the remains of another crossover trap.

I have a feeling that this system has been... ah... um. Let's just say worked on.