[vrechek]

Fun stuff, especially 57 years later. I noted -
Sugar's Bible from 1977 has the last series starting at #525,
Beckett #3 from 1981 starts it at #507 (as per the Topps checklist #509)
Beckett #14 from 1992 starts it at #523
SCD Catalog from 1999 starts it at #523
SCD Catalog from 2016 dodges it all by going from 447-576 for the high series
PSA today starts it at #523
No one much bothers with the reprinted checklist #509 issue.
Len Brown of Topps mentioned to me the need to match up the bases in this set like they did with the 1953s to avoid base colors bleeding over to where they shouldn't be.
Just looking at the last printing, it sure makes sense to me that they likely printed #509 along with #512 - #576 to have 66 cards with nicely matched bases - 22 of each color. I don't think the circle insets were as critical since I see some from an uncut sheet in the first series that don't all match.

Interesting also that the extra 11 cards mentioned in Series 5 are all found with cropping variations.
Yes, the bases should match up - except when they don't as in the case of #21, #28, #40 and #105 which seem to have some wrong adjacent base colors on miscuts.