Admitting I have not read Steve Hull's excellent book cover to cover, I am a little mystified by an Onoto pen I have just acquired. It has an 18ct nib. No other vintage Onoto of which I am aware has other than a 14ct nib.
The pen itself is one in the Streamline style. I will identify it properly later. The mottled red hard rubber barrel is labelled "Onoto The Pen" under which is, less clearly but present, "De La Rue & Co London", so that part is all correct.
The nib has a heart breather hole characteristic of the brand and era, but whereas my nearest comparable pen has on the nib "DeLaRue // Onoto // London // 3" (most others insert "14c" between Onoto and London) this one has "DeLaRue // London // Onoto // 18ct"
Has anyone encountered an 18ct nib on a vintage Onoto before?
I can not say how it writes because the plunger washer is fossilised, jamming the plunger. In other respects it seems intact, although the slip cap is either a ring-in or again very unusual, having slight knurling around the top edge but otherwise apparently normal in appearance and matching the pen for colour and pattern.