And of course post-chinagraph came the Stradeler(sic?) felt tips to which BE able referred. Two flavours, water soluble, easy to wipe off with spit and glove and a hazard in rain, and the permanent which one could, with care Sniff ☺ and could be cleaned off using the highly volatile solvent in a red SO tin until the HSE police banned it.
These allowed a finer line but both versions had the disadvantage that they would dry out if you left the cap off. They were much used by the Route Nav in Nimrods, not much use in a FJ in the air.