The blue G10 Manix, in new condition with box, etc., sells for maybe $220 or more. As a collector or reseller, you'll have to decide if its worth your Brown PM2. As a user, I would definitely get one of the cheaper Manixes. I think the tan Manix with M4 steel is still available at retail, for example, in the maybe $140 range (?), or even a regular entry level Manix 2 to save yourself some big bucks.
And make sure you are talking about the blue G10 Manix, not the lightweight clear/blue Manix that sell for $70 or whatever. Big difference.
But a blue G10 Manix 2, if new with box and paper, is probably a fair trade for a similar brown PM2. In fact, you would probably be getting the better end of the deal, at least in terms of street value. But if you want to use that blue Manix, you would be better of just using a less expensive but comparable Manix.
Just my view of the world, which is not worth all that much.
