To assess a violin, consider qualities such as tone woods, varnish, craftsmanship and repairs, and sound and playing characteristics. You should also consider the age and providence of the violin when purchasing older violins.
One of the things to look at is the wood. Check on the grain of wood used in the body, neck and scroll of the violin. Fine to moderate grain is generally a good indicator of quality.
Varnish on the instrument is another feature to check. The use of nitrocellulose lacquer or synthetic resin is common in mass-produced instruments and is a sign of low quality.
Next, examine the instrument for repairs and the quality of repairs. Finally, play the instrument to determine whether the sound suits one's personal preference.