Admiral 30A14 Cabinet Window Question

[fixmeplease]

Now that it finally warmed up I am refinishing the cabinet on this set. It has the normal clear glass in front of the CRT, and there is a tinted piece between the clear glass and the CRT. I dont see it listed on the parts list but know they updated this model a lot. Is that tinted piece original? If not original, would there be any sane reason to leave it there? All I can think of is I have to run it brighter to make up for it being there. Thanks!