1977 Schlitz "Stained Glass" Lighted Sign

I found this item -made by Everbrite Electric Signs, Inc.- in San Francisco about three years ago. I immediately found it attractive with its decent take on immitation stained glass.

The 25.5"H x 21.25"W x 2.6"D wood-grained plastic frame holds a white plastic back-piece containing two hanging cutouts and wall-spacers, and three factory Union/UL/Jos. Schlitz Brewing Co. stickers (identifying this sign as part #86522). This back-piece is lined internally with a wrinkled (for increased lighted effect), reflective foil and has mounted to it two galvanized steel pieces -one of which makes up the fixture base with two 11-watt (working) bulbs and the likely original gold/green grounded power cord attached. The second steel piece is simply to limit the hanging cutout's depth.

The front part of the mix is a two-piece layered deal with a six-textured, multi-colored (from behind [a decal?]), translucent plastic "glass" up against a well done, lead-like plastic framework replete with "soldered" connections where they ought to be -everywhere! This piece is still covered with its surely well-earned dust, though continues to look great in a bright room or lit up in a dark one. It's the only beer sign I own, with a 40s-era(?) Schmidt's "beer keg" tap handle (found at my now-past grandmom's house in Philly) rounding out the collection. As if I haven't described this intricate sign enough, any more info would be welcome! I wonder what the value might be. Also, is this something that is okay to clean (albeit gently), or just left alone? I know the lighted effect will improve with removal of the caked dust/film. Thanks for looking!