Jeremy
Here are 27 subjects in the 1910 COUPON set which were NOT printed with these following 350 series backs…..
CAROLINA BRIGHTS, EL PRINCIPE DE GALES, OLD MILL, POLAR BEAR. But were printed with the TOLSTOI back.
Do we have enough imagination to figure this strange incongruity, or is this a case where....
"Only the Monster Knows !" 
Byrne
Charles
Donovan (throwing)
Doolan (fielding)
Fletcher
Hoffman (St Louis AL)
Howell (portrait)
Huggins (portrait)
Huggins (hands at mouth)
Hunter
Killian (portrait)
Knabe
Lennox
Marquard (portrait)
McBride
McElveen
McIntyre (Detroit)
Mitchell (Cincinnati)
Mowery
Myers (bat)
Paskert
Rhoades (hands at chest)
Rossman
Schmidt (portrait)
Starr
Street (portrait)
Summers
TED Z
T206 Reference
.