During the late 1950s and early 1960s, I used Osmiroid pens and nibs almost exclusively for sketching and writing. After retiring, I decided to take up pen and ink sketching again and remembered my Osmiroids, Alas, the firm had closed down but I did manage to find an Osmiroid Artists' nib unit on eBay. Also, someone in FPN had posted that the nib unit screwed perfectly into Koh-i-Noor / Rotring Rapidograph Technical Pens, Model 3050 (or maybe 3060 - not quite sure) from around 1950/60. eBay came to the rescue again and I'm happy to report that the Model 3060 Rapidograph and the Osmiroid Artists' Nib have functioned perfectly for a couple of years.
There are several Rapidograph 3060 models on eBay right now and this is a good image of one.<<https://www.ebay.com...FgAAOSwdjdaLbV->>. The pens are piston fillers and usually uncleaned. Because they were technical pens, they were often used with pigmented (Indian) inks, which clogged and gummed up the works and threads, making it difficult to take the pen apart to clean it thoroughly and swap the nib.
If you get a dirty, jammed up one, (you'll know because you won't be able to unscrew the nib unit) I've found that the original Windex window cleaner works just as well as most pen flushes/cleaners. The main lesson is to be patient and give the lower half of the pen a good, long soak. There was a good article about cleaning these pens on the web <<https://crythebird.c...apidographpens/>>. Probably a year ago, someone had two of these Rapidographs for sale on eBay that had been fitted with Esterbrook nibs.