If the self-filling pen hadn’t been invented yet and you were considering ways this might be done, it’s likely that you would think about the syringe. It’s a method that has been used from the earliest times right up to the present. It has its failings and it’s hardly an elegant solution, but it does work. What you would be extremely unlikely to come up with, I would suggest, is a syringe-in-reverse, a filling system where the pen fills on the down-stroke of a plunger, but that’s exactly the method that De La Rue developed for their Onoto pen in 1905. It’s a stroke of counter-intuitive genius. Not only does it arrange to have the handle of the syringe in the tidy “down” position, thus eradicating the main objection to syringe fillers, it’s done in such a way that little barrel space is wasted and the pen holds a large charge of ink. In addition, a secure cut-off valve is built in, which also allows for regulation of the ink flow. It’s a complete solution to the problem of getting ink into a pen, which leapt fully-formed from the mind of the ingenious engineer George Sweetser and was perfectly implemented by De La Rue.
De La Rue were well aware that they had an exceptional design and they went on to make the Onoto the most prestigious and esteemed pen in the British market. Huge world-wide sales followed and the Onoto plunger-filler remained in production in the UK until 1955 and for a few years longer in Australia. It was succeeded for a few years by the K-Series open and covered nib piston-filling Onotos, nice pens but hardly to be compared with the plunger-filler. There were also some handsome lever-filler Onotos, much sought-after now but not accorded the same respect by the purists. De La Rue also made non-Onoto lever-fillers. Perhaps I’ve been unlucky in the ones that have come my way but the quality of these pens seems much poorer to me.
Whereas Sheaffer’s later implementation of the plunger-filler, the Vacuum-Fil, was never intended to be serviced and requires fairly major surgery to be restored, the Onoto was designed to be easily disassembled for replacement of the seals. Actually, provided the seals aren’t allowed to dry out for long periods, and filling system isn’t abused, there is a very long interval between seal replacements. I have an Onoto that I bought in working condition twenty years ago that’s still filling perfectly with the same seals. I’ve restored a few, mostly for my own use, but I don’t do Onoto restoration commercially. There’s a surprising variety of models, which makes for a very large spares holding, and spares are extremely hard to source and very expensive. Too much of an overhead for me, but there are several excellent restorers out there and I’ll be happy to recommend one if you need some work done.
The Onoto plunger filling system remains one of the cleanest and most efficient to this day. Onoto nibs are a delight. The pen was made in many styles and patterns over the years, so there’s something for everyone. The manufacturing quality is always impeccable. The Onoto is one of the best pens ever made and if you will forgive my own personal bias, THE best!