Recently I got a Schlumpf Mountain drive , for my Brompton ..
the low range is as if the crank which has a 54t chainring also has a 21.6t chainring too .
50 / 20 is even numbers .
they use a 3 speed hub twice, but the % differences between a 58" gear and a 23" gear ,
being the N or 2nd gear in each range, at 75% and 133% are smaller in low range ..
no indication if the VO setup even works , as shown, since the half step gear
wont shift out of the smaller of those 2 higher chainrings to the upper/ outer ,
with that, a MTB FD that needs a 12T difference just to clear that chainring.
Those half steps used a shallower back plate FD to clear something with only a 4 or 5t difference.
Cyclone road even offered a lower stirrup accessory to clear the chain
when it would drag on the usual Bolt and spacer at the Bottom tail of their standard FD cage.
But as a Conversation piece, see what it started.. ? that part worked..
LBS has a 59cm Specialized Expedition from the Mid 80s, on consignment FS, here,
it still has the original parts on it including the 48-44 half step + a granny crank
and 7 speed 13-32t freewheel.