"By golly Jim you've got it"....a very astute observation by you....congratulations.
I just looked over my all-Sovereign set; and, the 61 Subjects (including the 6 super-prints)
normally found in the 350/460 series have "apple green" backs. In addition, Nichols (batting)
also has an "apple green" back.....this card is thought to have been in this series,
Furthermore, this lighter green colored back is not found on other Sovereign cards in the 150,
350, or 460 series.
I will provide comparison scans of the 6 super-prints in my next post here.
Other series......[...........................sample of 350/460 Series cards.........................]
darker green.......[........................................apple green.....................................]
TED Z