Thanks for the response and link--yes that is my question. In digging further, I see it is established that the R311 glossy photos were issued in at least 1935, as evidenced by an ad piece Leon posted some time ago that stated as much:
http://www.net54baseball.com/showthread.php?t=198771
These were probably not available as premiums with the 1934 set, since Joe Cronin is shown wearing a Boston cap, and he was not traded to the Red Sox until after the 1934 season in October. So the various wrappers that list the players found in the glossy set are probably from 1935, which then begs the question of why no wrappers from 1934 are known, at least to OC.
R312 shows a photo of Joe Dimaggio from Comiskey Park and it seems that some or all of R312 was issued after April, 1936. The R311 leathers and R313 are likely from 1936, since both contain a Joltin' Joe card from Spring Training in that his rookie season, but I believe the latter (Fine Pens) may have been spread over more than one year and/or were likely given with the Batter-Up cards. I am hopeful someone can point to other evidence out there that better pins down when these premiums were printed and issued.