@bdp24 Sorry if you felt I was churlish. Just trying to set the record straight and it's probably something I picked up from Roger himself after many years of listening to him trying to set people straight about all things audio. He certainly didn't suffer fools gladly.
The ESL direct drive amps designed by Roger were never meant to be a product per se. The first ones were actually designed as a custom project for some Acoustat owners down under who wanted to replace the pitiful step up transformer that was originally designed for the various Acoustat full range ESL models. Roger appreciated Strickland's ESLs and they influenced his ESL designs. Roger was also very familiar with the Acoustat direct drive amp and designed a tube input stage modification for it that a few folks have benefited from. So he designed an all tube direct drive putting 5000V on the panels without that pesky interface for those very lucky Acoustat owners.
When Roger decided to build an ESL of his own, the earliest of which I knew of was around 2003, it wasn't used with a direct drive amp and it wasn't full range, it only went down to 100 Hz (as it was with all his other ESLs) and was biamped. I remember going over to his house to pick up a box for my RM-9 and he invited me in to listen to them with none other than Kavi Alexander who had dropped off his Beveridge ESLs for Roger to fix. It wasn't until he built the direct drive amp for the Acoustat guys that Roger built one for his ESLs (which required less voltage, I think around 3500V).
I would have to say Roger's last "product" was the RM-9 Special Edition. Limited to 20 pieces it is an all point-to-point wired circuit using an additional pair of driver tubes, 6BQ7s at that, and adding another 25 watts of power. Just about everything else was the result of custom orders and small batch efforts (ex. EM7 amp). Even the OTL 1 amp had only 6 pieces produced (on a RM-200 top plate where Roger didn't even bother to hide the RM-200 logo).
Roger's idea of "product" was very different than industry norm. He felt that as the designer he could make changes whenever he wanted without having to document or re-badge the designs. This is why there are 4 versions of the RM-10 MkII sitting out there. He kept most everything in his head but in the final year we pulled enough out of him to hopefully bring forth some posthumous designs that audio enthusiasts can enjoy. So yeah, in more ways than one that ESL direct drive amp was not Roger's final product by a long shot.