Cheshire

Japanese eyedropper filler with a shutoff valve?  You unscrew the blind cap a bit to back off the end of the rod and allow the ink to flow.  These were developed in Japan to deal with high humidity and I don't know who knows about these besides Ron Deutscher (sp?) and he's no longer active.

Agreed it does remind me of a JPN eyedropper filler from a few of the ads and photos I've seen online. I asked stan (Moderator on FPN) if there were any repairmen for them and yes they are as long as you ask them beforehand. It's interesting but I haven't tried writing with one before yet. Are there any markings on the nib itself? 

Alright thanks because I didn't find anything online about it other than old sales. 

Alright, good to know that my FPs will be be fine in their boxes. 

The other day there was a No4 Keyhole nib on ebay - I did bid on it - only because it's pretty - I don't own a Waterman's pen!  It went for £35 and it looked very nice indeed.  Sorry I cannot find the listing.

 

Cob

I do sometimes see spare nibs for sale but I wouldn't know which nibs fit each pen. To check old auctions that you didn't win it should be under Summary>Buy> Didn't Win. I like to use it to as reference for sellers and prices for pens.