The Zep was the name used by Montgomery Ward on their top of the line steel Hawthorne model between 1937 and early 1940. In the summer of 1941 the name was dropped and the model was replaced by the Hawthorne All American.
The Zep models used the same Hawthorne headbadge as the lesser models but had features that separated it from the rest of the pack.
Montgomery Ward sourced their bikes mainly from three sources at that time; H.P. Snyder (the Rollfast people), the Cleveland Welding Company (the Roadmaster people), and Monark (the Silverking people).
Over the time the Zep model name was used it fell on three distinct bicycles. The first version was only supplied by Snyder while the second and third versions were manufactured by both Snyder and CWC.
During the time that the Zep model was produced, Hawthorne named the second in line model the Comet (this name was also used after the Zep had been put out to pasture).
Like the Zep the Comet model varied from year to year and was produced by more than one manufacturer.
Long lead in but the bike in the picture is a Cleveland Welding produced bicycle. Not all of the versions of the bicycles manufactured for and sold by Montgomery Ward were shown in the catalogs and this is one of them. The only depiction of this frame being sold as a Hawthorne is in the 1938 Summer catalog where it is depicted as the Comet and is shown with a tank.
The paint design on this bike marks it as later than the one shown in the 1938 Summer catalog (several bikes identical to this one have turned up) so this bike is probably a 1939 model at which time the similar model with that paint scheme shown in the catalog is a Snyder built bike.
While the Comet name was used on the early bikes of this type, by the time the later ones were produced the name had been moved to a different bike (a lesser version of what had been the 1938 Zep)
In conclusion this bike is a Hawthorne manufactured by Cleveland Welding, it is likely a 1939 model and by that time would have been offered below the top named Zep and Comet models.
CWC did produce a tank that fits this frame but it is my guess that it was only supplied on the earlier bikes and not the later ones with paint schemes that match the Snyder version which was sold tank-less.
For more about the tank check out this thread:
viewtopic.php?f=34&t=24587