7 1/2 ft LONE RANGER wood MOVIE BILLBOARD ? s

Hi, I am trying to get some information on this LONE RANGER painted on wood. We have had this in our possession for over 20 years. What we were told about it is that this was part of a movie billboard to advertising a Lone Ranger movie. may be from "lost city of Gold". This is signed in the lower left corner

Clayton Moore The Lone Ranger 9-14-75

….The story we were told about the signature is that this piece was at an antique dealers roadside shop & Clayton Moore (already "retired" from the Lone Ranger role) saw it & signed it.
The measurements are following:
7 1/2 FT in hight
4 FT in width (@ bottom)
5 1/2 FT width (of hat )
The paint is beginning to flake and, as pictured, has chipped off at some spots.
and it is missing the right shoulder piece. Any info we can receive regarding this piece and possible value would be greatly appreciated. I am having difficulty finding info on just on vintage billboards... Any info? Thanks!