One of a kind - Hand Painted Buckeye Beer Sign / Proof

I have a (not just rare) but one of a kind, hand painted Buckeye Beer sign/proof that I am interested in selling.
The actual art is 21 3/4" x 9 5/8" and the board is 24 1/8" x 12".
It is mounted on chip board (like the printers used to do) and has been covered with a plastic sheet until I sliced the masking tape and opened it for better examination.
I believe this is an original proof to be taken to the printer. It is definitely hand painted with cut and paste areas (by the "B" and other places on the sign) but I don't know if it ever made it to the printer.
There are pencil lines by the "everyone's lips" area so the painter could stay straight.
I know this sign was made in Toledo Ohio, home of Buckeye beer and has been in my showcase for about 20 years.
I believe it to be from the 60's. Whenever Buckeye just started to bottle their draft beer, but I am not sure.
I have my thoughts but I would be interested in what you think it may be worth and/or if you want to make an offer. I have other photos I can email. [email protected]