Blue, halfway through the double pulley the crankshaft extension ends. The splined part that protrudes only goes in that far, and there seems no reason to ever remove it, so it is likely to be a heavy press fit in the pulley, and the pulley and splined shaft extension is probably only sold as an assembly. The retainer would then only be holding that ballrace in place, so there is no reason to remove it at present. I agree the retainer is probably a light press fit, like the rear axle shaft bearing retainers you referred to.
Incidentally Blue, you being an HT afficionado, I take it you are aware of what caused the failure of the last surviving couple of HK rally cars in the London to Sydney rally? The car body and suspension were reinforced so they could stand all the fly-and-fall activity, but the rear axle shafts were only retained by those standard pressed and staked rings, so when the axle shafts flexed on landing after each flight, the flexing made the retainers gradually wriggle off, allowing the axle shafts to move through the bearings, which increased their overhang, until the shafts fatigued and broke. As usual, a sixpenny part let down a whole race-team. It was a very long time ago, but from memory they had a large US-built Salisbury axle in those cars, and because it was intended for a rather heavy car, the engineers just believed it would be up to the job. No really harsh development testing, so the engineers didn't understand in detail how the cars would be driven.
