The older drivetrain works excellently and is pretty interesting. The hub is a "Sturmey Archer 5 Star Gear System," controlled via dual shifters. The way this is explained to me, it is actually two hubs in one: a 2-speed, controlled by the left shifter, and a 3-speed, controlled by the right shifter. The resulting gearing is a 5-speed rather than 6, because one gear (neutral) is redundant.
While Brompton did not offer a lowered gearing option in 1993 as it does now, it was possible to achieve this aftermarket by replacing the chainring on the Stronglight crankset, which is what the bike's owner did here. The gear range works nicely on hilly terrain, including on the 10% pitch I encounter on the way home from town.
Any owners of early Bromptons out there? Curious what you think of them compared to the newer versions.