Before Wheaties featured professional baseball players on the backs of cereal boxes, the company sponsored minor league sets for the Minneapolis Millers and Seattle Indians in 1933.  The cards measured 4" x 5 3/4", with sepia-toned images on the front, along with a postcard back that included an illustration of a Wheaties box.  Like all the unmailed examples known today, this one features a "VOID" stamp in the postage box at the upper right corner, the reason for the "MK" qualifier assessed by PSA.  Aside from that, this example - considered the key to the issue - shows a faint wrinkle and a light stain on the reverse, along with some corner wear, though the grade seems extremely conservative, given the excellent eye appeal of the card.  A small spot to the right of Hauser's bat knob, near the upper-right corner, is a dark surface blemish of some sort, and not a pinhole.  The key card to a scarce and seldom-seen minor league issue.