I like them too! But they're hard to find on my side of the Atlantic. Here's some more information on construction I received from the present...
The Dogger and Seahorse designs both seem to have a fin keel, while this one is a longer keel with an attached rudder, similar to the Trintels....
I registered here just to ask this question, because half of the searches I've done seem to lead back here, and it seems to be the place to ask...