It appears the Davis (as in Walter C Davis Aircraft Corp. Richmond Indiana) is the same as the Davis DA-1 at Rhinebeck. Same configuration, same Warner Scarab radial engine as a D (or DA) 1-W .
In my earlier I stated the Doyle /Vulcan was a biplane, which is incorrect, they were all parasol or shoulder wing aircraft. The geniology appears to be Doyle brothers O-2 Oriole, a parsol powered by a radial engine/O-2 special with a Martin engine, then then the Vulcan V-3 based on a de Havilland Moth then the V-3 morphing into the D (or DA) 1 in different forms (mostly it appears different engines and a different wing configuration). All the D (or DA) and V aircraft had radials except one V-3 refitted with a Cirrus engine.