[jimonym]

Jim,
I don't have a scan of Adkins+EPDG, just the entry in my notes that I've seen it at some point.

SRS,
I'm glad I'm not the only one who's gotten a headache from trying to figure this stuff out.

I think in general there are two drivers for front/back combinations.

One is timing. It's clear that some cards were pulled from production (e.g. Lundgren (Kansas City), Cross, Rossman, etc.) because the player changed teams. It's clear that other cards were late additions (e.g. Demmitt (St. Louis), Elberfeld (Portrait, Washington), Dahlen (Brooklyn), etc.) for the same reason. Given the wide variations across the 350-series I also have a very hard time envisioning that it was released all in one batch at one point in time. I think a much more likely explanation is a rolling release of several groupings, over many months. Then add to that different brands coming in and out of the process as distribution vehicles. I would suspect that most of these Old Mill backed cards were released early in the 350 series, before the T210s got started. Then after a hiatus from T206s, Old Mills were used to distribute them again nearer to the time of the release of the 350-460 cards. Hence, late release cards like Dahlen and Elberfeld being found with Old Mill backs.

A second is the way the printing was done. There were millions and millions of these cards printed, and certainly many thousands of each of the 350-only cards. I find it hard to believe that every example of a given card came from one printing plate, simply due to the volumes they were producing. As soon as you allow for more than one plate as the source of a given card all the neat groupings that might, based on back patterns alone, tell us which cards were produced together slip away. And several headaches later I can attest that there isn't much that's neat in the 350-only series.