I have a Westinghouse brass bodied vent valve and I want a second. My valve has T846 cast into the body under the Westinghouse logo. Handle is steel and swings through 90 degree arc. Threaded for 3/4 inch pipe. This is a very garden variety valve and everyone probably has a few. It was common on passenger cars and cabooses. Where can I find one? In my case, the application was on a passenger car platform for emergency or backup use.

The T846 is quite likely either a heat or pour number from the foundry (less likely) or a pattern number (more likely). A photo would be helpful to figure out exactly what you have. Since it's brass, it's likely an older product, as most of the newer stuff is now plated with clear or yellow chromate.

Yes, from my understanding the T-number is a patern number. Appearently, Westinghouse Air Brake did not distribute a list linking patern to part numbers.