I have a strange older lens: a SOM Berthiot wide-angle for Contax mount. It might be a post-factory conversion, but it doesn't have any markings to indicate the fact (as Roger Lemasson, for instance, seems usually to have marked his lens conversions).

I think I'd like to get it appraised, mainly to find out whether its value as a collectible greatly exceeds its value as a shooter. (It's a perfectly usable lens, but nothing miraculous, and I shoot very little 35mm anyway.) The appraiser would need to be fairly well plugged in to the strange-European-lenses market, as this isn't really normal stuff even in the collectible world---Berthiot lenses for Contax are pretty thin on the ground in general, and I've never seen *any* other example of this particular lens.

I've never had an appraisal done for anything that wasn't a house. How does this work, and how do I find someone who can do the job competently?

Much thanks