The Jack Knife Safety Pen was a fore-runner of sorts of the Duofold. I say “of sorts”, because the name doesn’t so much describe a model as a feature. Like many other makers in the early days of fountain pens, Parker used model numbers to describe their pens, and it seems that Parker’s numbering was more than normally impenetrable. While a number will describe a set of features, and there are occasional glimmers of a system– a No. 23 is smaller than a No. 25, for example– there doesn’t appear to have been a real organization to the numbers and it seems that they reflect the order in which the pen entered Parker’s catalogue as much as anything else.
The Jack Knife pens appear across many model numbers, and what distinguishes them from their fellows is the construction of the cap. While the term “safety pen” currently implies something with a retractable point mechanism, the original meaning of it was a pen you could carry around without destroying a whole suit of clothes. In the case of the Jack Knife, this safety feature was accomplished with an amazing innovation– an inner cap. This is a very standard feature of fountain pen design, it was a patent-able thing at the start of the 20th century; interestingly, the patent was applied for in 1909, but wasn’t granted until 1912.
In fact, the Jack Knife inner cap is a little different from the usual inner cap. Rather than a simple tube, the Jack Knife’s outer wall tapers away from the inner wall of the outer cap, which would help to prevent capillary action from allowing the ink to migrate from one to the other, thence all down the section, from there onto the writer’s fingers and eventually the doilies of the maiden aunt he’d hoped to impress into increasing his inheritance. Parker’s advertising of the time shows men carelessly putting pens in any pockets they might have, with accompanying text exhorting him to “simply, without thought or danger of leaking, shove it in any pocket you want and always find it ready for instant use…,” in much the same way as one might do with a jack knife. I will merely raise an eyebrow at the wisdom of tucking a brittle rubber pen into a trouser pocket, but otherwise the principle is sound.
The line, or rather the name, was retired in 1925. The arrangement itself continued to appear in the Duofold until its initial retirement in 1933.
Production Run: 1909 – 1925.
Cost When New: Varies by specific model.
Size: Varies by specific model.
Point: 14K gold.
Body: Hard rubber, and possibly also Bakelite; the caps and the material definitely overlapped in Parker’s catalogues, but I can’t confirm whether both appeared in one pen.
Filler: Eyedropper or button, capacity varies by specific model.
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