...well, there seem to be a kazillion violin afficienados keeping a close eye on eBay for `treasures`. Odds are that if it is indeed valuble, someone who knows what they`re looking at will snap it up...
...having said that, you still can get lucky, but the odds are extremely slim...also keep in mind that there are an awful lot of awful antique violins out there!!!
They weren`t good when they were new...and they`re not improving with age either...
...often time people will try and unload these poor quality instruments on eBay and hope for the best...
...check out the seller closely, see what the feedback is...ask them questions...
...and good luck!...