Perhaps that reference is to a split flange or upset nut? There are many locking type nuts that don't use a nylon or fiber insert.
“When a long train of abuses and usurpations, pursuing invariably the same Object evinces a design to reduce them under absolute Despotism, IT IS THEIR RIGHT, IT IS THEIR DUTY, TO THROW OFF SUCH GOVERNMENT...” -Declaration of Independence, 1776
From page 5 of my parts manual. Chemical Surface Treatment. The manual shows S CST. Or Steel, Chemical Surface Treatment.
In my world, Carbon STeel. As opposed to SS or PSt
back then it was probably not nylocks but the all steel type. I prefer the all steel type as they seem to service better later on. nylocks I have had gaul up on me. I would switch when rebuilding.