What do I have?

[nikonhswebmaster]

I just measured the outside of the smallest part, and I see 31mm on my micrometer.

Interesting, so it was only there for assembly of the lens? Not to mount a filter. I assume the adapter was a lucky after thought, but really have no actual info.

I am surprised no one on the RFF has shown us a complete set. This was supposed to be a great lens.

 

[wes loder]

m-b adapter

m-b adapter

The first 55mm Micro-Nikkor for the Nikon F was a preset lens. The close-down ring was also the filter-mounting ring (52mm Nikon F standard). This meant that any filter would rotate when the lens was stopped down. It also made it difficult to reverse-mount the lens on a bellows. The M-B ring screws into a smaller thread well inside the front of the lens (31mm) which does not rotate when the lens is stopped down. This allows the reverse mounting of the Micro Nikkor on a bellows and still easily stop down the aperture. The second version of the pre-set Micro Nikkor has a projecting filter thread that eliminates the problem. The M-B ring was not a good solution since over-tightening the ring and then trying to remove it could cause the lens to unscrew (oops!).
You have a very rare item. I own one and use it to adapt a telescope eyepiece to any Nikkor lens with a K-3 ring. WES

 

[Waus]

Thanks again for the input!

 

[nikonhswebmaster]

This meant that any filter would rotate when the lens was stopped down. WES

That is the missing piece of information!

I could not remember why the adapter was needed.

I have handled the lens and put in an adapter, but nothing more. Any idea how many were made? Did it share elements with the rangefinder version? I cannot find a lens diagram.

 

[nikonhswebmaster]

Wow - how in the world does that place stay in business. Those prices are ludicrous.

As I always said to collectors who made that comment, go buy at the cheaper table, why bother me?