I'm liking the plotter subject at the moment.
One of my fondest memories was I think circa 1988 at college. We had the "technology club" in which we got to piss around in the labs and build whatever we wanted basically. This exposed us to a pile of test gear, dangerous chemicals (we had a PCB fab at hand!), spanking new BBC Masters, several hundred quid's worth of lego and some Dacta control boxes. And this gem in a book:
The software that came with it was crap so I had the fun job of writing something. It was mostly BBC BASIC nudging bits in the user port but some of the loop based timing routines weren't very precise so the kettle and the inline assembler was fired up. I ended up inventing a control language for it which wasn't that far off postscript which was funny because I had never seen postscript before then.
The result after several evening's work?
(but I learned a lot and got to play with lego)
Edit: with respect to pens we used Berol felt tips, attached with a rubber band with a load of blu-tack around them to give them some mass
Edit 2: also a minor flashback. We used to steal stacks of electronic components from the college stock room. They knew, to the point one of the tutors said he did and that he'd face the other way and read his newspaper while we helped ourselves, because it kept their budget for tech department allocated