44 AMP, if you can still obtain photos of this firearm from your friend, I would very much like to see them. I have never seen one of these guns in person, and the only photo of one that I've run across is the one that Steven Mace linked to from the Vest Pocket Pistol collector's site. It would be really nice to see pictures of another specimen.
Could you possibly ask the gun's owner how and when he acquired the Mann, and, if he is willing to divulge the information, how much he paid for it? I have no good idea of the real value of something like this (which I'd like to know in the highly unlikely event I encounter one for sale). I have found that my Blue Book 29th Edition, much to my dismay, doesn't concern itself too much with the more obscure old pocket pistols
By the way, has your friend fired the pistol?
Any info/anecdotes about this fascinating little gun would be great!