As a guide, I recently sold this:
Originally Posted by jafo
which I would have graded conservatively Exc+ (perfect except for two small scuffs on the side of the body). What I got for this was around half of what I paid two years previously. Prices of all collectors' items except for the absolute blue-chip specimens seem to have gone down, one problem with old finders is that they usually have a plain metal rim at the rear - this means that anyone old and aflluent enough to think of buying these will in fact not do so for fear of scratching their eyeglasses!