Wiss better made scissors and shears were (and actually still are) "inlaid." Basically, just as Matt said, the "inlay" is high carbon forge welded in to form the cutting edge.
It's just Wiss' name for a procedure used in making a lot of other tools, more commonly called "laminated." All of my broad hatches and broad axes are made this way, and all of my old mortis and firmer chisels as well. Come to think of it, my old blacksmith bench shears are made this way, too.
Good looking job on those snips, too. I like 'em!