Conditions Affecting Lens Value
I believe used camera lenses should be judged on a combination of cosmetic condition and functionality. This is in addition to the original sharpness, clarity and contrast of the lens when new. I also know that people value lenses in distinct and different ways. For instance, a lens in mint cosmetic condition, but not functioning, may be perfectly acceptable to a collector. On the other hand, a user may not care much about the appearance of the lens barrel, as long as the glass is free from scratches, fungus or clouding of any kind -- and it works. The table below lists my general rating categories for both cosmetic value and functionality of used lenses.

Cosmetic Condition		Functional Condition
Rating	Cosmetic Description	Rating	Functional Description
Mint	New in box with original warranty, or as new, never used, with absolutely no signs of wear.	Mint	New, everything functioning perfectly. Still has factory warranty or seller guarantees functioning.
Excellent	Very minimal signs of wear. If it had a box, you'd have a hard time telling it from new.	Excellent	Everything functioning well. Recently professionally cleaned, lubed and overhauled.
Very Good	Barrel may have signs of slight use, but not abuse. Glass is very clean.	Very Good	Major functions recently tested, and seem to be functioning well.
Good	May show signs of normal use or age. Glass is clear (antique or rare lenses could have light cleaning marks).	Good	Fully functioning, but not cleaned or overhauled recently.
Fair	Complete, but showing signs of heavy use. Lens glass may show light, inoffensive cleaning marks.	Fair	Usable, but not fully. Aperture may stick at some settings.
Poor	Restorable. Refinishing may be required or truly necessary. Minor parts (not glass) may be broken or missing.	Poor	Not usable without repair or cleaning. Aperture sticking. Lens glass may have light fungus or light cleaning marks.
Parts	Major dents, dirt or abuse evident. Glass broken or cracked. Consider major restoration effort only if a truly rare lens.	Parts	Everything damaged, nothing works, major parts missing, glass bad. Probably not worth repair. Toss, or use for parts only.