KC's right again
'''''I think it's a typo or wait a minute maybe it's in British nits. '''''
you all should know about their '''old world threads'' to confuse the germans.
BSF
BSW
MA
CEI
BA
BSP
all different threads and pitchs as well as wrench sizes.
all types of Whitworth
http://www.sizes.com/tools/thread_history.htm http://www.jag-lovers.org/xk-lovers/library/whitworth_system.htmlI have sets of every type here, too

they were so far ahead of themselves it left our heads spinnin'
by the way joe
they have dark suckers too
http://www.msu.edu/user/dynicrai/physics/dark.htm 
I believe that .86 to 1 and .73 to 1 are two ratios (for 5th gear) that were standard in models. mine is .86