Two long bolts pass through from the rear plate and screw into the front housing. If you don't want to do a full teardown hold the main starter housing in a vise and carefully unscrew the through-bolts, but leave them in the field frame while you ease the nose cone and drive off the front. The shift lever will remove with the nose cone and take the drive with it. On a 12V starter, the drive splines on the armature are spiral, so the drive gear will rotate a little as it pulls off. If you pull the armature out of the brush assembly you'll need to do a full teardown to get them back into position.
Jerry

"It is better to be silent and be thought a fool than to speak and eliminate all doubt!" - Abraham Lincoln
Cringe and wail in fear, Eloi- - - - -we Morlocks are on the hunt!
There is nothing noble in being superior to your fellow man; true nobility is being superior to your former self. - Ernest Hemingway
Love your enemies and drive 'em nuts!