I'm trying to find a hose connector for draining the water from the baseboard heater return.

I spotted these things, I believe it's a kinda old drain valve, does anybody know it? I'm talking about the coupling with round small and larger cap.

If a regular hose goes in the larger connector, it seems weird, since I need to shut off the water after the hose to drain it.

This is the water return side, from top to bottom.

Thanks.