I'd probably use 1144 steel; I'm not sure what that might translate to in South Africa.
As for procedures, I think I would start by chucking a bar of appropriate diameter with enough sticking out to make a collet, and completely turn and finish the o.d. When the o.d. is done, part it off and put in the collet chuck to finish the nose where it was parted off, then drill/bore/ream the center hole.
As the final step, mount it on a stub arbor in a dividing head or spin indexer or whatever, on a milling machine, and as much as possible cut the slots with a slitting saw. You probably won't be able to cut them completely because you will run into the stub arbor and have to finish the slots by hand.
Note that I have never actually done this, but it seems like a reasonable sequence of steps to me.
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