Karl Hurth GmbH of Munich Germany developed the original small sailboat gear back in the late 1970s and they really came into their own by the early 1980s; displacing the larger and heavier hydraulic units. Kanzaki (a.k.a. "Tuff Torque") made some units jointly with Hurth and from what I gathered back in the day, promptly copied their duplex clutch mechanism. A lawsuit ensued and I do not know of the outcome. In any event, Karl Hurth sold his company to ZF in the early 90s and the rest is history.
From looking at the image, my best guess is that it is a copy of a Hurth HBW 50 or 100, but do not take my word for it. For a more authoritative answer, I would contact a fellow named Chris Hughes. He owns Atlantis Marine Gear in Topsfield MA and has forgotten more about all types of marine gears than most people know. AMGS was also one of the original Hurth distributors. Hope this helps.
