The Great Escape

Okay, I've figured out the Exit to DOS command:
Press Esc to bring up the restart game prompt, and from there press Q to quit.

Does anyone remember what the keyboard command to quit the game and exit to DOS was? I haven't played this game in decades, and the few retyped manuals I could find online make no mention of an exit-to-DOS key/combination.

We never beat the game when we played it. Apparently, there was one key we didn't find because it blended in too well. I've watched videos on YouTube of people completing the game; this is like an interactive fiction game, in that once you solve it, there's little replay value, but manually controlling your character and trying to avoid the guards adds a thrill into the game that interactive fiction lacks.