The Hewlett-Packard 7475A is a 6-pen plotter from 1983. It can draw on either A3- or A4-sized paper (configurable using a DIP switch on the back of the unit) and speaks HP-GL over either an RS232 serial port or HP-IB (each 7475A plotter has one of these interfaces, but not both).
These things are really cool to watch while in action and are practically indestructible.
I wrote a tiny Python script, hpglplot, to plot HP-GL files on RS232 variants of this plotter using software handshaking (so you can use a simple three-wire serial cable or a cheap USB-to-RS232 adapter without any problems).
- HP 7475A Technical data (PDF, 60kB)
- HP 7475A Operation and interconnection manual (PDF, 1MB)
- HP 7475A Interfacing and programming manual (PDF, 3MB)
- HP 7475A Service manual (PDF, 1MB)
- Cenon (a useful multi-platform program for converting various vector formats into HP-GL)