These rather plain Waterman pens turn up quite often. They have no name or number, and resemble the last, celluloid version of the Waterman 52, cut down, without the lever box and a little more streamlined. They’re not fancy but they’re good, and I buy them whenever I can. Guessing that they’re 1930s pens, they’re more robust than Waterman’s output would be ten years later, they’re well-balanced and comfortable in the hand, and they often have exceptional nibs.
Talking of which, this is from the guarantee/instruction leaflet in the box. Quite a range of nibs were available for this humble pen. First time I’ve heard an oblique called an “SSO” and I’m still not quite sure what distinguished a “TUP” from other nibs.
It would be my guess that the “Flexible Fine” was fitted to this pen!