OP & dynaryder can Pick up a copy of 'the Brompton Book' it is quite informative of the changes over the years ..
David Henshaw's Brompton Bicycle|review by Tony Hadland – NYCeWheels.com
FWIW, Sachs 3 speeds are 0.73,1,1.36 - BWR 0.64,1,1.57. - AW/BSR .75,1,1.33
Last edited by fietsbob; 03-16-16 at 03:54 PM.