Kirk, did you do a search for Black Letter at lets say MyFonts or even a Google search?

Kirk, I think you may have to deal with the real possibility that this is a custom lettering job. That G seems absolutely simplified from any blackletter G I can find. The 'a' is also very different from most blackletter fonts. A lettering artist would have only had to make 5 letters to create the whole word, and a font would never have been needed. I even looked at Photo-Lettering types, which could have been the source if '19??' was earlier than about 1988 when digital types started coming into wide use. My catalogs of film types probably don't show everything, and the other source, the Solotype Catalog, doesn't show a match either.

If it has to be exact, why not just use their existing art?