Rare J-3 ?

[xayraa33]

is this a rare J-3 lens, that it came from the factory with a J-8 type focus section?
or did someone cobble this up on their kitchen table?
notice that the DOF scale only goes to F2.

http://hosting.westernbid.info/images/uploads/leon1965jazz/j32.jpg

 

[xayraa33]

Leon has had this up for a while. Don't know about the mount, the thing that worried me was this (what is this?):

that looks like the focus cam guide that is found on the older tabbed J-8.
I wonder if someone screwed in a complete J-3 lens module in an older J-8 focusing unit, if that is possible?