Assuming it is a Juzek, and you cannot go by what a label says as it only takes a minute to install one, it then depends on if it is a real one or a copy (that is, one of the commercial ones). There are not many of the real ones and they sell for over $5000 and they were made in Prague Czechoslovakia in the early 1900's, so I am assuming that it is a commercial one. The commercial ones from the 30's-60's are factory made in Germany after the company moved its Prague location and generally sell from $350-750. This price range depends on the quality of the wood, the condition and of course the sound. The Juzek line is still made and distributed by Metropolitan Music but they are a cheaper quality of instrument and the three models range in price new from around $300-450.
As far as the signature goes, even the commercial copies that were made use a label that is a copy of the original Juzek instruments and these labels can be copied from a number of books even today, so just because you see a signature does not mean that it was actually made by John Juzek. The original Juzek labels had some Red Printed color on the label that the factory ones did not.
It is always best when buying a violin to deal with a violin shop where you can get a warranty, a trade in ability and a place to deal with if it needs repairs. If you are looking at it from a private individual, I would recommend that you try to get it on approval to show your teacher and you can also take it to a violin shop for an appraisal. You never know, I have had customers that bought yard sale instruments that turned out to be worth many thousands of dollars.
Retired professional violin maker and repairmen w/ 35 years experience in the retail violin market
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