Looks like they were the rarest of all the 20' models. Check out these links to the literature section - lots of good info there that many folks on the forum don't even seem to know about!
Production numbers 79 Brochure
There is also a cross section view of all the later models in the
Specifications link. Check out the Sceptre 23 Hardtop/Flybridge models! Anyone ever seen one of these?!