I picked these porcelain double sided gas price signs up at a yard sale a few years ago. I thought they were cool, and had to buy them lol. There's 27 pieces total, and all are double sided with a different value on the other side. Can anyone tell me what they're worth, about what years they're from and maybe the brand of station or type of sign that held them. They are 3 7/8" wide and 7 7/8" tall. I'd like to try to find something to be able to display these, so any info is appreciated. Thanks!