Oh wow! You have one too!
I managed to acquire one of these dropped seat stay Sun's a year or so ago. Very rough condition though and it's bene tinkered with over the years.
I think mine is running a British Hub Company coaster brake on the rear with a Resillion centre pull/canti on the front. A nice Williams crankset with a Benelux 4 speed derailleur and shifter. The bars and stem had been swapped out for some of the townie riser style bars though.