Is it steam or hot water heat?

Hello,

Forgive me for these basic questions. My dad could have helped, since he's an old ASHRAE HVAC engineer but passed away 2 years ago.
I have a home from the 20s in CT. I have cast radiators, an old coal to oil burner, and lots of big low-hanging steel insulated pipes in the basement. We're looking to clean up the basement-maybe replace the monstrous burner.

I know this is hard without seeing the system, but:
1- Can it be determined if this is a steam or hot water system? Radiators have 1.5 inch(?) steel pipes on each end with a valve on on side,a bleed valve, but no steam valve that I can see. Could this have been a steam system but now is hot water?
2- If this is hot water but used to be steam, since my dad did teach me hot to sweat pipes, can I start replacing the basement steel piping with copper, in anticipation of getting rid of the ancient boiler/burner and replacing with something more efficiaent? I was thinking of working from the radiators back, trying to keep the copper pipe diameters reasonable.

Thanks for any tips or insight.