PLEASE NOTE: I will not be able to answer any questions about antique keyboards, accordions, concertinas, woodwinds, brass and percussion.
I can answer most questions on fretted instruments, my main area of expertise is in vintage mandolins, guitars and ukuleles. I also know some things about old banjos as well.
I have decided to no longer evaluate instruments -- it is very difficult without the instrument in hand. For guitars and some other American fretted instruments, I recommend the Vintage Guitar Price guide. Also, be aware that most insurance companies want written appraisals so my valuation would not work anyway.
ALSO PLEASE NOTE: it is near-impossible to accurately appraise a violin or bow remotely. If you truly want to find out what you have, you will likely need to take it to a reputable local dealer. Many of these folks will at least give you a verbal assessment of what you have after an inspection in hand and, if it is indeed worth something, can write you up a formal appraisal, usually for a fee.
If you have any questions about zithers please check the following sites:
Between the two of them, they have it all covered for any zither-like instrument.
I have been buying, selling, collecting and playing old and antique instruments for over 30 years. My recent specialty has been in European mandolins and classical and Italian mandolin music.
Classical Mandolin Society of America, active participant on the Mandolin Cafe
Guild of American Luthiers, Sing Out Magazine,
BA, Brandeis University