The H&S 1952 super set was 579 and I know some 52 collectors on the board have expanded that number. A good many of such additions are recurring print defects or variances. In my view there will never be a finite number for any master set because there is no standard definition in the hobby of what constitutes a variation that should be included in a master set.
I think many collectors would use all or some combination of variations listed in SCD, Beckett and or the Registry to define a master set. The gray backs are a big hurdle to a master 52 set, as well as 2 Mantles, Robinsons and Thompsons
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I broke the line on Topps but so far staying the course on Bowman.
Always appreciate it when Ted pops in over here