Chinagraph.
ricardian,
(Your #12) - without Chinagraphs no ATC Tower in the land could have functioned in the '50s, '60s and early '70s ! It was to the AT Controller what his trowel is to the bricklayer.
The propelling Chinagraph was particularly useful: it stopped you having to hunt about for a pencil-sharpener (and busting the end through overdoing the sharpening). Got one somewhere still.
Eraser ? Fag-ash (in ready supply then) and a bit of cloth.
Our perspex "Arrivals" board in Approach was back-lit, the Assistants got very good at "mirror writing" with white Chinagraph on the rear surface.
D.