What is a stub nib?

In current usage, a stub nib is a rounded italic: its point is wider than it is thick, but its profile is smoothed for easier writing. There are those who object to this definition on historical grounds -- a detailed discussion can be found here -- and as it turns out, the confusion of what "stub" means goes back quite some time.

The passage above appears in Waterman's Circular No. 55-25, which can be dated sometime between the later part of 1898 and 1900.