Hmm, if you are looking for more desirable Gerbers as future trade bait or re-selling then the following might be useful (based on my own personal opinions, I haven't done an in-depth comparison of current sales prices):
Any "First Production Run" Gerber Mts are more valuable than later variants.
The older Mr Pinchies didn't have any locking tool components and were all steel. Most had blunt nose pliers, the very early ones with polished finish on the handles are sought after.
Later MP600s had plastic locking tabs (mostly black, some grey), most had blunt nose or needle nose pliers
The oddball variants are usually more valuable eg Fisherman pliers, Cable Cutters, TrailRider (hoof pick), Coloured handles, prototypes.
The MP650 with swappable plier heads are usually more valuable than all except prototype Gerbers. The full Military kit with all heads are very much in demand.
Watch out for the numerous cheap chinese copies (usually BO with CC pliers), these can be sold as genuine (often by sellers who don't know any better)
The only MP400 I know of would be the Fisherman (really long needle nose pliers)
I hope that helps.
babola: "Enjoy your tools and don't be afraid to air your opinion and feelings here, but do it in courteous and respectable way toward others, of course."