What you have here is almost certainly a copy of a Stradivarius which has an average current market value of $75 - $400 USD at auction or in a private sale depending on the quality of the reproduction and its current condition. However, there are some reproductions that can bring up to $8,000 if made by certain manufacturers, but these of course will be labeled appropriately with that manufacturer’s name. Since it appears that yours is not, it most likely falls into the first provided price range.
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Alan C. Ransdell, AOA AM, CA