Date is probably August 1940
According to Volume 2 of the Maytag Collector's Club manual, production of the "E" started in late October 1939. Therefore, the earliest date of the photo could be the following August, in time for the Wisconsin State Fair.
Another interesting note from the manual: The last gray Model E was serial # 109528-L and was produced Dec 11, 1940. Initially, the models were "ELW" for white, or "ELG" for gray. The "L" designated electric, or "M" for multi-motor (gasoline). Later when gray was no longer offered, the "W" and "G" were dropped.
Mystery solved on the round tub machine on the left - it is a Model 108 (Jan.1939 - Apr 1941). Notice that the wringer head is not typical. It was, in fact, outsourced and made of sheet metal, not cast.
The all-white round tub on the right is probably a Model 110 (Jul 1934 - Jul 1939). They were typically painted blue-green with a tan lid, but some of the last production models were all white. (this information courtesy of Volume Two, again).