Chev steam valves

[huphuphup]

I am working on a '43 HUP and was hoping to reach a consensus about the steam return system. The pictures and books just show a line coming from a fitting in the rear of the cylinder head. My engine has a small pot metal valve at the head fitting marked Binks No. 57? The story is that you opened this on steep dissents to relieve trapped steam in the rear of the head. I have a hunch that this valve was added as it is covered in brass parts and the idea of it being accually used is unrealistic. Anybody know?