Posted By:
RobertSThe card in question was issued by "Burk & Attwell" (not Burke), the same folks who also issued a Philadelphia A's premium, as well.
Moreover, the Sox cards I've seen (two to be exact) were not postcards. One was blank-backed (see below) and the other had a stamped ad for a restaurant. Most importantly, the card is larger than postcards of the era. It most likely was a premium.
This doesn't mean, however, that Lew's card isn't a postcard (as he puts it: "what appears to be an excellent 1912 Burke & Atwell postcard"), although it, too, is likely blank-backed.
I've seen the Sox card go for $500 within the last two-three years, btw, but since I've only seen two transactions I have little on which to base an expected price for another.
Here's an image:
For a larger version of this image (in which you can read all the player names and the publisher credit line), you can visit this Web page and simply click on the photo to enlarge: http://www.vintageball.com/WhatsThis.html
I hope this helps.