This is a weathered patina porcelain/enamel HARLEY-DAVIDSON dealership sign.
No markings so exact production date is unknown. It's heavy, thick, convex, 20 x 18 inches of rusty gold - used and abused by years of having been exposed to the elements, with a finish that's still slick and blinding. Just the way we like'em!
A must for any man-cave, bar, garage - or better yet, to replace that horrible family picture over the living room fireplace!