At first glance I'd guess either Mercury or Steelcraft (both are Murray Ohio products), or Garton. It does have similar design features of both companies. The handlebar looks like a Mercury design and the frame looks like Garton. Hmmm...this trike really looks familiar. Seems I've seen a photo of one just like it years back but can't recall where. I did some Google searches and couldn't come up with a match. It is definitely from the later 1930s. This is going to bug me until I find that photo again.
Dave