The 1926-29 Exhibits "Postcard Back" issue is speculated to have been issued in the Philadelphia area.  Though the cards typically feature postcard backs, they are occasionally found blank, and some with the notice "Not for use in Exhibit Machines."  Further, some contain a country of origin (USA) added to the backs.  The cards can be found printed in a variety of color tints as well.  The result is a wide variety of possible variations with differing degrees of scarcity, very appealing to advanced hobbyists.

Outstanding midgrade example with a pink tint, graded VG/EX 4 due to wear on the reverse.  The card front appears NM, with sharp corners and virtually no signs of edge chipping that comes with the color tinting of many Exhibit cards.  An outstanding example.