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Stradivari, although he was a prolific producer of stringed instruments, never made bass fiddles. What you have is a 'tribute" instrument, a workshop instrument, most likely made in a factory in Germany at the turn of the 20th century.
If your bass fiddle is in good condition with very good tone, its current retail (replacement or insurance) value is approximately $1,200.
If you were to sell it, you could expect to get the fair market (private sale or auction) value of 40% of the retail amount, or approximately $480, depending on location and actual condition.
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