People ask - Why do I assign numbers to all my pens, nibs and inks. Well it started out as a database geek thing - you know everything has to have a UID (unique identifier).
For my nibs that reason still stands but by numbering them all I can keep track of where they are so I can get them back to their original body if need be, see, I like to swap my nibs around my pen bodies where I can. This started right from day one as I had three Lamy Studio bodies and a set of Lamy Z50 nibs ranging from EF to 1.9mm italic. It got worse when I started buying Pelikan pens, their nibs are made to unscrew easily, and you can even to swap nibs between models, e.g. a M6XX body can also use nibs made for M400 & M250 pens. Therefore a M600 pen body in my collection has currently 30 nibs that could be used with it.
Due to my love of custom grind nibs, in most cases I have more nibs than pen bodies for any given style. Where do I keep the spares? Filed away by its nib code of course. I use little boxes containing file cards each have a plastic zip lock bag stapled to the back. (see image below). They keep them all neat and tidy.
It all makes sense to me. :)