Need some help. A friend gave me a Buick sign as gift and I'm pretty sure its a repo. She got it at an antique store and the guy told her it was real. Its a 10 3/4" painted tin sign. Says Authorized Service around the edges. Buick across the middle with Valve above that and In Head below. Not sure what she paid for it but don't want her getting ripped off. Thanks for any help.