Originality can sometimes be determined by a careful examination of interior markings, and a measurement of medallion placement in relation to the edges.
At big $$$, any knowledable buyer will want inspection priviledges.
If you intend to sell them, be prepared to have clear, close-up pics, of the backs of both grips, in addition to pics of the faces - preferably with a small rule laid alongside them, in the pic(s).