When Sheaffer introduced its "working togs" utility pencils in the late 1930s, they quickly became a very successful seller for the company. The robust design and exposed eraser made them a perfect no-fuss writing instrument, and the company sold millions of them over the course of decades. Sheaffer also came up with a thinner lead for use in these pencils, called "Fineline" lead, and eventually created the "Fineline Division" dedicated to producing lower-cost writing instruments, including the "pearlie" pencils, up into the 1970s.
Sheaffer's success did not go unnoticed by Parker, so Parker decided to try to get into the game. Parker's response was the "Writefine," and the earliest examples strongly resemble the "wartime" or "striped" duofolds of the early 1940s:
The Sheaffer influences are impossible to ignore: exposed eraser, strong middle joint mechanism, even a ribbed lower barrel. The clip is very similar to what is found on the Wartime Duofolds:
My research has not yet led me to any conclusions about whether these were offered with or without a clip; however, on these early examples the top unscrews, so it's easy to remove a clip, and I suspect my "clipless" model has simply lost its clip somewhere along the line.
The most interesting thing about these early Writefines is the plastic, which is red and blue. Here is a Writefine, in the center, flanked by a pair of Wartime Duofolds:
Writefines are red and blue, while its closest Duofold relatives are either red and grey or blue and grey.