let's say it's XF in details, but dark.. if not flat out ugly? just round it down a few notches i suppose huh... a net grade... but how far down, and what determins that?

What kind of coin, papadoc?

Copper could be the planchet material (Classic Head US Large Cents, for example) or poor storage ... too much sulpher in the environment, etc.

let's say Lincoln's..

regardless of the standards i have to assume that if anyone pays for a VF, and got an ugly XF would be disappointed.. maybe if they paid VG.. i have no clue hence the thread i guess ha

This is always a problem for me - net grading. If it is naturally dark from age (so called "original surface"), I say you certainly lose eye appeal points, but far less than if it were cleaned. Hypothetically, an EF40 details becomes maybe a VF30-35 - something like that. If it were an EF40 details, but obviously cleaned, I go VF20. Personal preference, of course.

sounds good... man i can't stand those cleaned coins.. but something tells me that there's gotta be some people out there that love it and would consider it a score. that's inexperience or they're 85 years old or something, so nevermind that.. it's just painful to look at a really detailed coin with an unnatural look to it.. and selling them feels like a gamble every time...

especially those vf/xf black coins... or with the red 'paint' look... or with the 'gold' streaks all over it..... speaking of lincolns.

A fellow I do a little business with from time to time sold his 1895 proof Morgan. It was black as tar and still brought top dollar. Dark toning on a coin doesn't change the grade, it's just notable if you're selling it sight unseen. Key date Lincolns seldom get net graded because of dark toning or for any other such mild loss of eye appeal. Some people even like dark toned bronzes.

Now, common date Lincolns are a different matter. Those get culled for minor reasons, I've noticed.

Try a UV Lamp I hear them UV rays are good for anything.