That's the Southern California 3 speed club:
http://www.threespeedtouringclub.com/
The motto is "cycling for pleasure not penance". The site has links
to those 50s British videos. They are worth a few minutes viewing
time.
It's a spacious tent; British content not req'd and wear what you
want. At the last event James showed up with his Riv sporting a
single cog with a triple crank, qualifying it as a 3 speed. Andy
brought his Atlantis so he was limited to a single cog to avoid
disqualification. Our response to the obvious question "What is the
point of all this?" is quite simple: Lunch!
FWIW, the instigator of these shenanigans sometimes ride a 4 speed but
it's hard to tell.
dougP