That Magna ink-visible I mentioned in an earlier post came with a pleasant surprise. On commencing disassembly I found that the shank pin appeared to be metal under a little hard black wax. That was a surprise. Clearly the pen had been restored at some point. The section having been removed, before continuing to remove the shank pin I worked the stiff piston again. There was a satisfying pop of vacuum release, meaning cup washer and rod seals were in fine condition. A bit of silicon grease on the piston rod and barrel wall, and it is working perfectly, ready for ink.
The odd thing about both this Magna and the black one is that neither wholly conforms with the table on p 217 of Steve Hull's book, nor information in the text or photos. Both are marked 1873 yet both have a single wide gold band, the [sole] distinguishing feature of the 1876. An 1873 is supposed to have three narrow bands.
Purportedly, pre-war Magnas used 14k gold bands whereas post-war used 9k. The black Magna has an 18k band hallmarked De La Rue. It was probably a special order or else a frankenpen of Onoto's own making (accidental, careless, or somewhat deliberate) during the difficult post-war era, or else toward the end of Onoto's corporate existence. The single tone nib which this pen has were apparently characteristic of very early or else late production.
Ink-visible Magnas are presumed not to have been produced after 1940, yet mine has a 9k band hallmarked Johnson Matthey & Co. JM&Co apparently provided these only around 1946-1948. The year code is L but I could not find a reference to date that properly. One auction site as an item with code M which they date to 1946, so I guess 1945. The solution I think most likely for that puzzle is that production did indeed cease in 1940 but the pen remained in stock, being sold post-war when there was access to gold again and the band was fitted. Nib is two-tone.
When you receive new information you can change your mind, or you can close it; or you can try shooting the messenger.