The rear "extension" on a Richards ring is not completely "round", meaning it stops at the sides of the frame. The Recoil Shield (frame behind the cylinder) is cut back exposing the channel for the hand and the arbor is screwed back on holding the conversion ring in place. The hand is replaced with a 2 stage hand and the cylinder after being turned down, in the rear, has had the ratchet teeth advanced from the centerline of each chamber to between each chamber. The hammer nose is cut to accept a fixed firing pin then later the sight cut off and a sight machined into the ring and the firing pin moved there also.
Regards, HH