Help identify air system part

[RocketScott]

That's a simple quick release valve, QR-1. When air is applied to the front brakes it sends that air to both sides equally. When pressure is released it allows the air from the brakes to exhaust through the bottom of the valve in stead of going all the way back to the treadle valve

You can get a rebuilt kit for it but it's cheap enough just to replace it. You'll need to match the size of the ports to the old one. I can't quite tell from the picture what size they are

ETA- If I had to guess I'd say 1/2" supply port and 3/8" delivery ports. Hard to get a sense of scale in the photo