Two Dunlop 4D 200 16x19 's bought at different times of the year from different sellers. Small differences in serial numbers should be expected right? ---> YMVLCA on first racquet. ---> YMVGC13S on second racquet. Balance, weight, everything is spot on between the two, aside from some very small imperfections in QC- (Dunlop stamp is off center on one) but why the variation in serial numbers? Any thoughts would be greatly appreciated.