Another light followed me home. Best way I can describe it is a wall pack looks brand new. If I deciphered the date code correctly, it is a 1975(?) Mercury vapor 250 watt.

Suggest you upload this to the gallery, it will probably get more views there 

Another light followed me home. Best way I can describe it is a wall pack looks brand new. If I deciphered the date code correctly, it is a 1975(?) Mercury vapor 250 watt.

Looks like a GE WL400, but the back of the housing is different...it might have a different designation.

Looks like a sign light !

Yeah, I think you're right.

Nice.

Is it really a sign light though? It does look light an older Wallighter but I could be wrong about that.

It's definitely an older Wallighter. This luminaire was originally launched in ~1967 and was simply called the Tunnel & Underpass Luminaire; it utilized the rounded housing as shown above. Starting in the early 1970's, it was renamed the Wallighter 250 while still retaining the rounded housing. In the early 1980's, it was renamed again as the WL-400 Wallighter; also, the rounded housing was superceded by the modern square housing. Sometime in the 1990's, it was renamed yet again as the Wallighter 400 with the order code of W4L. It was then discontinued in 2017.

Hope this clears up the confusion.