All violins you buy from ebay or luthiers or auction houses should be examined carefully and critically. There are only fakes on the market. With a lot of famous names like Pressenda, Rocca, Poggi, Guarneri, Landolfi etc. Sometimes i look to an old violin in London (i will not let you know the name of auction house) and think... how it comes that this piece of sh... sold like for example italian violin by landolfi. If you have auctions with no reserve you can buy for honest prices. In case instruments have estimate price you should be sure - you will never sell for the same price. The best way you fly to the seller/auction house/liuthier and check violins personally.