Tom, I love these traditional daysailers and have come very close to pulling the trigger on one of my own over the years, hence my awareness of the subtleties. That alerion in your picture may be an older one built by Sanford as they did a number of them with the Gunter rig as shown. Alternatively, it may be a custom one-off.

Some production fiberglass versions with a bit more house (vs the cuddy in your photo) like the illustration you posted, have been built by several different builders. Briton Rieff built several from wood/cold molding that we're more like the fiberglass versions. I think he also did a traditional version much like the one in your picture based on Herreshoff's original Sadie. They're all fun boats.

Despite my love of them, we're going back to the multihull side as practically, they're more appropriate for how we really want to sail and where we really want to sail. These are the better reasons for choosing a particular design. But, if I lived in Maine, there would be a slightly larger version of the BB 18 sailing around.