That's really interesting. That card does not look right to me. The print quality is lesser than I would expect, like a second generation card.
Also, the back cardboard looks too coarse for an Exhibit card.
I always thought this Gehrig image was taken later and used on later cards. Like for this 4 on 1:
or the W517
Then there is the Gehrig batting and Gehrig silhouette.
I don't know of any silhouette card being preceded by a second pose.
The portrait used to make the card needs further research. Here's why:
--MEARS sold an 11 x 14 portrait from The Sporting News as a 1925 Conlin (7/31/2011 auction...for only $118!).
--The 1991 Conlin cards list it as a 1927.
--It is in the book about Conlin's baseball images too: does anyone have access to one?
Anyone got a handle on other Conlin resources? If we can pin down the date the picture was taken we can rule out any earlier cards using it.