It’s hard to get a certain date for the introduction of Swan’s SF1. I’ve seen 1917 quoted and that’s possible. It’s obviously early because many examples come with New York nibs, so it pre-dates the establishment of Mabie Todd’s nib works in Britain.
Perhaps a little slender for modern tastes, in every other respect it’s a delightful pen. Though the illustrated example was a firm needlepoint, most SF1 nibs are flexible. Some are very flexible indeed. Posted, it’s a long pen with good balance. It comes as a plain black hard rubber pen, but also in mottled hard rubber and with a variety of gold trims. All in all, it’s one of the best and most practical of early lever fillers.
From my point of view, however, the SF1 has a down-side. It’s the only Mabie Todd pen I don’t like to work on. The tolerances on this pen are often very tight indeed, and it’s not difficult for the repairer to break one. The section fits into the barrel very snugly, and it requires a lot of heat and patience to get the section out. Putting it back in after the sac has been replaced is even worse, and it’s at this point that the dreadful “snap!” that can really spoil your day can be heard. It’s not that the pen barrel is especially fragile – it’s fairly robust, in fact, but the fit is unforgivingly tight. I’ve once or twice been tempted to plane the section down, but then I’d have to shellac it in, and it wouldn’t really be the same pen.
That’s the SF1 – a pleasure to use, a pain to repair!