This is an unused L&C Hardtmuth Airless fountain pen I purchased recently (7000 lire in the 1950s, it seems, and over-priced today).
The piston seal looks intact but is very stiff so I would like to grease it, whereon I discovered some interesting things on which I would like some advice. Pretty as it is, the pen itself has all indications of being something made for Hardtmuth by someone else, so in looking at further description and pictures, you may be able to relate it to something else German or East European, probably from the mid-1950s or a little earlier.
Close examination of the section through the semi-transparent barrel suggests that it is not threaded. However, heat and force to the limit I was prepared to take the thin celluloid showed no sign of give. I think it is glued.
I can chase removing the nib-feed assembly (it did not give easily) or try removing the piston. Before doing so, here are the curiosities (to me) and queries. The next two pictures show the piston knob under the blind cap (all pictures expand with suitable clicks):
From the second picture it appears that the knurled knob is not formed with the threaded part, yet when you turn the piston knob then the threaded part unscrews from the barrel as the piston extends. It is possible to work the piston fully (and very stiffly) by this means but it can hardly (to me) be intended operation because the celluloid into which it is threaded will surely soon wear and crack.
There is no flat or hole visible in the threaded or knob part, so if the inner knob is to release then it is simply a padded grip on the thread that would be needed while the knob is turned (after heating). I am expecting that the assembly is released by fully withdrawing the plunger using the inner knob (assuming it can be moved) then keeping it still while unscrewing the threaded portion from the barrel. By the way, knurling on the barrel is for effect only. Close loupe examination shows no join there.
Is anyone familiar with this piston mechanism, or seen the same in a better known pen? Do you think I should simply resort to trying to unscrew the nib and feed, returning to the piston assembly only as a last resort?
Thanking you for any assistance you may be able to offer. Edits for clarity.
Edited by praxim, 24 May 2018 - 00:03.