I hear what you are saying, and it makes sense. But I also think you are drawing on quite a bit of additional knowledge about tire-related advertisements that an inexperienced collector would not have. Even if I visualize a tire stand 40+ years ago, there is no memory I have that makes me think this 8x18 sign is a fantasy piece.
The bottom-line, unfortunately, is that if there is enough money to be made, a talented counterfeiter will find a way to make an aged reproduction that could fool many/most collectors.
