Now, Its a different.. wider ratio hub BWR.. the successor to the AW3 is the BSR
the 9 spline driver is another Shimano created standard on the BWR adoptedfrom Shimano's BMX hubs

the 3 speed uses the 3 spline cog that S-A has almost-always used .. the Mk 3, 6 speed Brompton went to Sachs , in Germany then,

they used the 3 spline cog type, in 3/32" thickness .. a different driver for their Torpado 3 speed .. to take 2 cogs ..
the 15t was made as a skip tooth .. 1 in 5 was shorter.. , so the chain would shift over it.

I use the 15t, alone, all that will fit .. on my M3L


(edit: N/M)