Can you identify this Nikon accessory?

[kkdanamatt]

I know that it fits under the rewind crank of either the Nikon F or F2, but what does the other end fit? It appears to have a single contact under the collar as well as a side contact on the collar.
Thanks for your help.

 

[xxloverxx]

Most likely something for a Nikon flashgun/flashbulb holder, as those were mounted on the rewind crank.

 

[not_in_good_order]

Try this link:

http://www.mir.com.my/rb/photography/hardwares/classics/nikonf2/flash/index2.htm