I collect mint, loose GI Joe's from the 80's (82-88/89).
I'm pretty picky about condition....."mint" has to be stiff joints, new paint, new screws...basically...it looks like it just came from a package. I'll take one or two little imperfections (its hard to find some figures 100% mint, the paint can be very delicate and flake, rub off.....some of the Cobra soldiers can be hard to find with 100% intact cobra insignias). Or guys like silver pads, grand slam...those guys can be very tough.
So it might differ slightly for different figures.