Standard Oil Company of Louisiana Stanocola Polarine Sign

I got this sign from my grandparents. It was in one of there barns when when they bought it in the early 60's. It is porcelain and double sided. The condition is not that great, probably because it was covering a hole in a barn for many years. I don't really know the value of it ,its not for sale I like in to much, but I am kinda curious about it's value, Thanks.