Swinging BB front wheel drive with a Sturmey-Archer 5-speed hub (an old one, with
a trigger control on each handlebar to control two separate sets of epicyclic gears!).

Mark's Comment; The right hand trigger puts you in 1st, 2nd or 3rd gear. The left trigger
determines whether the 3 gears are close or wide ratio. 2nd is 1:1 either way.