Clow gas steam radiator

lakota

Took me awhile but here are a few pics My question was someone gave me this rad I fired it up and there was a steam leak on a valve that is located behind the first section towards the top where my finger is in the pic.I tried to take it out but broke apart.What is this valve, someone said maybe a vari vent did they have them back then. what would I put in its place.