Since Esterbrook nibs are interchangeable, they can end up in some pretty strange places.

Here's an example:
http://tinyurl.com/2qtjwo
The icicles were late production and the 3*** series nibs with a flat feed were early! The icicle would more properly have a nib with the verticle numbers.

Another example:
I bought a "mint" desk pen (a lever fill, not dip) off eBay in the original box with the original instruction papers. The nib that was on the pen was a 5*** series dip pen nib! Great pen, great nib, but they didn't belong and in fact, wouldn't even have worked properly.

Most times it doesn't matter, but sometimes, it's just silly. Or maybe I'm just easily amused.