get a copy of 'The Hobbit' and you can work out the olde english runes. They appear similar (from what I remember of reading/writing them) to the anglo saxon runes on that
transposer. With one or two exceptions for certain letters/sounds: X, I & U used for J & V, CW for Q and some single runes for double letters like th, ng, ee, ea, st...
EDIT:
of course that was all a long time ago
Why don't we just use the enigma machine sim? then rogue skippers can communicate without bdu rapping any knuckles? lol