Looks like a piece of tape to me. Rod is correct on my groove to groove being .370" however that was on a model 96 in 9.3x57.
Seems to me, I read somewhere the 9.3x62's on 98's were more true to groove diameter of .366".
He is also correct on the guard screws, especially the rear screw with the steel tube. That tube will likely prevent the proper tightening of the action screw and thus can set back and crack the tang of the stock.