The notch in the cap represents the porthole of a submarine or a sight window and refers to Verne's 'Twenty Thousand Leagues Under the Sea'; in addition the cap shape is interpreted as an allusion to a diving helmet, and the symbolism is also found on the nib. The ink tank of the Jules Verne is in fact smaller than that of the 146, because the sealing piston in the limited edition — as on all editions — was structurally changed.