LARGE GM Genuine Parts Receiving Porcelain Sign

I was TOLD this is an original Factory/Plant Sign from a GM Parts Receiving Bay in Ontario, Canada. It is a 2-piece sign that measures 15' x 2' and is in Good condition. There are some rust spots where the Porcelain chipped off but it shines very nicely. I am thinking about submitting this to a local Auction House as I do no have any where to keep it since I moved. How mush is something like this worth?