I don't have that version here at the moment, but with many of these the optical assembly (complete with aperture) drops into the focusing mount and is held by a retaining ring. That is the way my earlier 8 element is.
Sometimes you can just rotate the whole unit into position by grabbing the front and turning, but don't force. This direction will tend to tighten the threads in doing that, so I think you are likely to need a spanner to loosen the retaining ring. If it is as I've described (just covering my butt), then it is a very simple adjustment for any repair person.
PLEASE DO NOTE: Not all Leica lenses are the same (though most lenses of this vintage and older do thread together in some way). In later lenses the optical unit is GLUED IN. You don't want to be twisting those!
Added thoughts - It won't hurt anything at all to leave it as is. Someone that uses a tripod may even prefer it that way. This has no impact of focus adjustment since the optical unit is not changing distance, just rotating on its base.
Last edited by Mark Crabtree; 11-27-2011 at 09:50 AM. Click to view previous post history.