NPB Card Guy tells me that the crossed bats set was issued over two series, and the flag back set was issued over 10 series.
With this new information, I've reevaluated my thoughts on how the set might have been released.
The bat-back set consists of two series. Were they issued together, or separately? If they were separate issues, were they available at the same time or one month after the other?
Bat-back cards (#1-91) and the first release of flag-back cards (#1-91) were probably issued early in the season - somewhere around April-June. The second wave of cards (#92-296) would have come around midseason or later, possibly in July, but maybe as late as September. The final wave (#297-368) was probably released by the end of the year, either November or December to include the Japan Series cards.
The 10 series for the flag-back set probably breaks down something like this:
- 1-45 (approximate)
- 46-91 (approximate)
- 92-136 (approximate)
- 137-209 (approximate) (137-173 and 174-209?)
- 210-236 Dragons Team (Tokai region release)
- 237-260 Osaka teams [mostly Hawks/Braves/Buffaloes] (Central and Western Japan release)
- 261-278 Lions Team (Western Japan release)
- 279-296 Carp Team (Western Japan release)
- 297-322 (approximate)
- 323-368 (approximate) Vs/Playoff/Japan Series
Series 1 and 4 contains several instances of players having multiple cards in a row (especially Oh and Nagashima). The remaining series have a broader selection of players, though several players have back-to-back cards. The ninth and tenth series overlap a bit, and could be one series; if that is the case than my fourth series would probably be split between card 173 and 174. I label the tenth series as the playoff and Japan Series series, though the games depicted on cards starting around #305 include important regular season games in addition to playoff and Japan Series games.
The first wave would be cards 1-91, with the second wave covering everything from #92-296. The final release (after the season ended) would have most likely included cards 297-368.
Keep in mind that there are a few variations in the set, which can be attributed to regional printing variations. With cards 210-296 apparently being issued only regionally, I wonder what children in Tokyo thought when they opened bags of chips with card numbers in the 300s!
If you have any comments about this, I'm open to your thoughts! This is based only on information from a few (pretty knowledgeable) sources and there isn't really enough detail to make more definite thoughts.