On Ebay is sort of difficult grading a pen, I have problems with it myself and even with my pens, I gathered some information from other sources/websites, to make something helpful, for myself and for others. Full Excellent vintage pen should have clean trim with (arguably) only trace high point brassing (smidge on a clip ball, etc), good imprint, solid threads, clean nib (though some grade nib as a separate piece), etc. Also, keep in mind that MOST PENS are NOT up to the Excellent grade. Various minor flaws do lower the grade, and should lower the price- but such pens are still very collectible. The trick is to pay the right price for the right pen. The trick is not to assume that because a pen costs a few dollars less at e-auction than in a reliable vintage pen-dealer’s store, then it must be a much better deal -though it might be 🙂

Condition codes

Description

Pristine Mint. PM = Untouched, unfilled. No marks or spots whatsoever. Crisp colour. Never filled. This condition rarely exists. Absolute perfect condition.
Mint. M = Perfect condition. No marks, spots or brassing. Crisp colour and shiny finish on plastic pens. No discolouration. Working condition. These pens can be filled. Not filled pens should be noted. NOS pens should be in Mint condition.
Near Mint. NM = An excellent pen, but with parts of duller finish or nearly invisible surface scratches. No brassing, virtually a Mint pen, but with small signs of usage.
Very Fine or Excellent. VF or EX = Visible, but not accented surface scratches or parts of dull finish. More accented scratches where the cap goes on the butt and body. Otherwise fully functional and crisp finish with no brassing.
Fine. FN = Visible surface scratches or dull finish. Visible surface scratches or dull finish. Signs of wear on the nib or light discolouration of the section or around filling lever or button filler. Light brassing or small lip crack. Clear signs of usage, but still a better than average pen.
Very Good. VG = Some scratches and dull finish. Signs of everyday usage on nib or body. Brassing, light all over discolouration. Minute lip or body cracks. Loose cap rings or body rings. A used pen in average condition.
Good. G = Scratches, dull finish. Nib and body well used. Brassing, discolouration. Small lip or body cracks. Light cap or blind-cap misfit. Loose cap rings or body rings. Worse than average condition, but still a fully functional pen.
Fair. F = Severe scratches and marks. Severe brassing. Discolouration. Small lip or body cracks. Cap or blind-cap misfit. Loose cap or body rings. Still functional, or functional with light attention.
Poor. P = Severe scratches and marks. Svere brassing and discolouration. Severe cracks or essential parts missing. Cap, bodyrings or lever missing or loose. A not functional parts pen.

INSPECT

WATCH FOR

Trim Brassing,Dings and Missing Pieces
Cap/Barrel Material
(plastic, hard rubber, or metal)
Toothmarks, Scratches, Gouges, Dings, Brassing, Detail Loss, Burns, Warps or Bends, Removed Engravings (names) etc
Gripping Section Damage, Overpolishing, 
Nib Missing Iridium, Cracks, 
Filler Unit Need for restoration. Missing Parts. Prior destructive Gluing. Etc.
Manufacturers Imprint light or missing imprint
Threads poor cap closure. (spinning cap, badly angled cap)
Repairs, sleeves on cap threads, etc.
Transparency dark ambering of clear portions of pens.
Color 
(Not all consider color to
be part of “Grading” pe se)
Discoloration, which has a big impact on value, independent of other wear and damage. Perfect “Jade” can be worth 5 times as much as darkened Jade
Other Hidden repairs- Sealed Cap Cracks, Removed Barrel Engravings, etc