Hi there! Welcome to my journal =) I thought I'd put this up at the top for you =)
The short story is: it would be really cool if it were, but I wouldn't get your hopes up. And you could have a very valuable violin there, even if it's not a real Stradivarius.
I'd be interested in what you find out. Do come back and let me know one way or another, if you're so inclined. =)
I'm no expert (to make an understatement =), but I do know that if this violin in your family has been played often and maintained properly in these last 100 years, it would be very very valuable anyway. If not in market value, then at least in sentimental value.
GET IT INSURED ANYWAY!! ... is my point. Make sure someone is making beautiful music with it regularly and taking good care of it. Don't let it sit idle.
As to whether it is a real Stradivarius, I'm almost certain it is not. Allowing for a little uncertainty, all real ones have been accounted for.
I don't know where you might get a proper appraisal. You could look for a violin repair shop in your area and ask to be referred to an antiques appraiser who specializes in stringed instruments. If you're in a big city, someone in your local symphony orchestra society might be able to help you out as well.
You really would want to know the market value for insurance purposes.
Good luck! =)