I finally have an answer to a question that has puzzled me for a while: where did the oblique holder come from?
It’s obviously not a product of the era of the quill, so when did we first have nibs held at this odd, oblique angle? To answer this, you first you have to go back to the Early Years of the steel pen: 1820-1860.
Prior to this period, steel pens were almost universally all barrel pens affixed to a holder pretty permanently. Pens were also not really disposable. There were even steel pen repair services, just like the same services to repair your fine quills.
Individual slip nib pens which fit into a holder were originally pieces of a quill which came in a box of nibs and fit into a holder. These were disposable and meant to obviate the need to mend your quills.
By 1831 you did start to see more what they called “slip nib pens” or “portable pens” (easier to carry than a long barrel pen), but the idea of holding the nib at an oblique angle in the holder was an idea new enough it warranted a patent.
In 1831, an enterprising and very successful stationer and inventor, Sampson Mordan (inventor of the silver mechanical pencil) combined with one William Brockedon to patent the first oblique pen and oblique holder. (I’ve attached the patent below)
In the patent application they mention as the benefits that this will allow the writer to hold the pen more comfortably as well as it should allow the pen to last longer since both tines will be moving across the paper evenly. If you read the description, the idea of holding a pen obliquely seems to be a new idea, and one that requires explanation and justification, and the obliquity itself is patentable.
“and we hereby claim as our invention, the oblique direction or position purposely given to the slits of all pens, whether made of quills, metals, or other fit and proper materials, and also the obliquity produced in the use of common pens, whether made of quills, metals, or other fit and proper materials, when held in our oblique pen holders.”
The holders shown in the patent document include oblique nibs, as well as oblique holders with straight nibs. Figure 17 is explicitly labeled as “another pen holder adapted for holding common quill or metal portable pens [slip nib pens] in an oblique position”