I have an old normark, lock back with wooden handle.  I like it a lot.  It has become one of those old friends.  It is probably as old as any gear I have.  It just feels right and I really like that it is a lock back.  Funny, I carry a fixed blade belt knife, but a lock back fillet knife, though the fillet knife stays in the tackle bag until needed.

As far as sharpening, I'm not sure what brand it is but it is a little plastic thing with ceramic "rods" in it.  You just draw the kinfe through a couple times.  That's what I have for trips.  At home I have an Arkansas Stone.