4x8 double sided reflective wooden sign

Think this is a pretty unique and early sign, measures just under 4x8 both ways. It is wooden, painted with the reflective glass sand and is double sided. Couldn't find a comparable sign out there. Anyone seen one before? One side has been sort of washed by the previous owner and the other side has not been touched. it will clean up a lot more. It has a split starting at the bottom running lengthwise but otherwise really solid yet. It looks like it may have had a frame around it at some point as well. Anyone out there have a clue?

Thanks Aaron