Uncatalogued by Burdick and still not correctly listed in the SCD Standard Catalog, this set was issued circa 1911 by the Chicago tobacco firm Spaulding & Merrick (later acquired by Liggett & Myers) as a premium with their Plow Boy long cut tobacco product. The set includes 42 cards + 1 variation – not 50, as is usually stated – of Cubs and White Sox players measuring 5 3/4″ x 8″ each. While very scarce, they occasionally appear in auctions at around $500-$1K for commons in decent condition. Most cards will have one of the two ad backs shown below, but there are also some that are blank. Click on any of the thumbnails below to see the full image of the front.
Dec. 2016: I have a very nice dupe of Purtell available for trade or sale.