As you say, the ampersand is distinctive, so I went through all my marks looking for a similar form. I found nine, all from Connecticut and most from New Haven. Looking then at likely makers of appropriate period and surname, I have:
Elisha Elderkin (New Haven)
Alfred Elderkin (Windham)
David Ellsworth (Windsor)
Jacob Jennings, sr (Norwalk)
Miles Johnson (Wallingford)
Only Alfred is known to have had a partner, John Staniford, c 1790.
I'm not sure this gets me anywhere and this is, of course, a restrictive survey given the nature of my project, but it may lead somewhere someday. Or not.