Ever wonder what made the world's first "luggable" computer tick? EEVblog has released a video teardown of the groundbreaking device.
http://www.notebookcheck.net/EEVblog-tears-down-world-s-first-portable-computer.187821.0.html
Actually you didn't need a strobe. All you needed was to be in a room with fluorescent lighting. The 60 was for calibrating in countries with 60hz mains (ie USA) and the 50 was for calibrating in countries with 50hz mains (ie UK).
There's a liner pot with a standard slotted screw head, you adjust it 'til the bars stand still with a floppy loaded and the head engaged.