Just in case anybody's not up to speed on this. It became available in 2011.
The std Sturmey pull chain arrangement has been replaced in this model by a rotary cam (Sturmey patent, 1970!), with the shift actuation inside the dropouts. The shift cable is simple to attach/remove with no unthreading/readjusting of anything and no loose parts when disconnected. The R-SRF3 has a solid axle not weakened by any internal passageways or cut outs, and the axle nut threads are 3/8" like Shimano rather than 13/32" like other S.A. hubs. Otherwise, it continues with Sturmey goodness: the beautiful polished hub shell, NIG, comes in the box with all the nuts, washers, cable, shifter, cog, etc you need to put it in service, &etc. The cable pull requirements to shift the R-SRF3 are greater than the classic AW family of hubs, and it uses a different (factory) shifter. Mine came with a dual paddle 'push-push' (RapidFire style) straight bar shifter. 130mm OLD to make room for the rotary gear select.