[Arran]

I seem to recall that 1937 was a "recession" year, so a greater dip in the midst of the great depression. I remember hearing it refered to as the "Roosevelt Recession" since it happened on his watch and it was believed that his policies were to blame (which they probably were in hindsight). In any event if Philco had misjudged sales levels and sales, and the economy had shrunk for two consecutive quarters, then it's quit possible that Philco would have had some leftover 1937 model year cabinets and chassis to use up for the 1938 model year.
Keep in mind that the model year for radios then was similar to cars, the new year would begin in the late summer or early fall. In reading Ron's book Philco typically shut down the production lines some time during the summer months, normally June I think, so if there were any leftovers in June they would be held over until the line started up again. So the early 1938 models would have been made late in 1937 and they would have been assembled with whatever they had on hand and ready to go at the time.
Regards
Arran