Artillery Luger grips - replacements?
 

I recently picked up an all matching 1917 Artillery in very nice condition. Upon examining the inside of the grips, I noticed that the insides of both grips are unnumbered but have a small "x" inside. The inside of the left grip is very rough, but the x is discernable. The inside of the right grip has an "x" and a very clear "2". I logically thought the left grip would have a "1" but I cant seem to find it. What does do the x's mean? Thanks!