Jabberwok, the photos I have show a DH60M on floats, circa 1930. The floats have rounded tops, similar to the Edo 2870, and they taper to a point at the rear, no transom. There are no water rudders fitted. The bottoms are not fluted, just straight Vees. The front spreader bar is in line with the propeller, and the step appears to be in line with the leading edge of the lower wing.
You might want to check out
www.flight-history.com/ . Check out the photo archives, or contact the moderator. She may be able to help.