Yes, you're absolutely right - by about 1959 nobody with any sense or money was still using a 'plunger' type derailleur. I'm sure that's why the final Simplex version was a hopeless failure even though Anquetil used it successfully. Aside from anything else it cost as much as the Campag Gran Sport, but still retained the old technology. Although I was around at the time I think the first 'Juyrecord-60' I ever saw was on Hilary Stone's table at a recent Ripley Jumble - and he wanted £300 for it!
I have in front of me an advert from Sporting Cyclist for July 1962 which offers the JUYRECORD-60 for 95 shillings (£4.75) which might sound cheap until you remember that you could buy a Campag for £4.00!
I have a feeling I may have retailed this story on here in the past, but I think it's worth
repeating. I got this from a Bath RC member who is a little older than me and as a young man trained with Dave Bedwell (AKA The Pocket Rocket from Romford). Dave was a prolific winner of road races and a successful pro. Some time about the end of the fifties when he had just spent an evening desperately trying to hang on to Dave's back wheel and they were warming down he said: "Dave, I can't understand why a man of your status and calibre is still using that crappy old Simplex mech."
Dave replied: "Oh that's easy, I get three quid a week to keep using it."
My friend was dead impressed, as an apprentice he was only getting £3.17.6 (£3.875) a week!