The Super Regen section of the 19 set apparently did work but unfortunately not very well
. It's been mentioned a few times over the years and there was at least one aricle in PW [I think] during the sixties re one valve re slope detection at VHF. Tanuki started a thread this year in March WS 19 'B' set. I've always had the impression that the Regen Type circuits lasted longer [as a working concept] in the USA but I'm not sure where I've gone that from except maybe, reading ARRL Handbooks!
Dave W