My grandfather bought me a violin at an auction. The person who was holding the auction asked for it back because it went for $50. He said that it was an antique violin from the 1880s. I don’t know if I can trust this source of information. The case has a GSB Violin Case emblem on the bottom. Where can I find information? I am desperate in finding correct info on this violin.
It is nearly impossible — actually it is impossible — to appraise an instrument via verbal description, even if accompanied with photographs — over the internet.
What you should do is take it to a reputable luthier. A luthier is a person who repairs, in some cases makes, and also appraises stringed instruments. There is usually one or more in every community. I would not indicate that you might want to sell it but rather, tell them you want to have it appraised for insurance purposes. Sometimes there is a small fee associated with this service, like $20, but they might do it for free.
See:
Requests to appraise an instrument
http://beststudentviolins.com/StringCareSpecs.html#2
An excellent resource for your violin lessons need.