If the first color fired on was black it makes sense then others laid on top just can't tell by pics. Pierce truck signs was white on back because that was base color with others added on top,just don't deal with a vast amount of companies. Doesn't have to be truck door sign maybe could be attached to rear of tanker or parade promotion sign would explain why no one has seen before.
Good Luck,so far you have a one off!


*Wanted Pierce Pennant Petroleum*