I have a note that I made once (but no reference for it) as follows:
	Engelbart chord keyset (with 5 long piano keys) used simple binary
	encoding (A=1, B=2, etc)
	use with left hand (right on mouse)
	looks like left thumb = 1's bit, index = 2's, etc.

	So it would be something like this (for right hand):
	A	1____
	B	_2___
	C	12___
	D	__3__
	E	1_3__
	F	_23__
	G	123__

	H	___4_
	I	1__4_
	J	_2_4_
	K	12_4_
	L	__34_
	M	1_34_
	N	_234_
	O	1234_

	P	____5
	Q	1___5
	R	_2__5
	S	12__5
	T	__3_5
	U	1_3_5
	V	_23_5
	W	123_5

	X	___45
	Y	1__45
	Z	_2_45

	sp	_2345
	lf	12345
	.	12_45
	del-ch	__345
	del-wd	1_345

I believe Infogrip "BAT" uses a different code, that they had thought
about carefuly, but I I don't have the code.  It's a 5-key chord
keyboard, sold as a replacement for a regular PC keyboard. Their web
site is http://www.infogrip.com/bat.htm but I didn't see the actual code
described there.

And I started once to make something like the one-handed qwerty
keyboard but using only 5 keys, like:

	Hit correct finger for qwerty keyboard
	Hit thumb for which hand you'd use on qwerty
	Then hit some other too, perhaps:
		nothing if home pos
		one extra key (lowest numbered key remaining) for bot row
		one extra key (skip lowest remaining, choose next lowest) for top row
		above + highest remaining key for horizontal stretch
		Don't use something that results in "12345"
		"Lowest" key does not include thumb

	It looks something like this, but there are some conflicts in it
	(marked "NOGOOD" below):
		FINGER	HAND (1=L)			EXPLAN


	B	2	L	123_5			12 + lowest + 3rd-lowest
	F	2	L	12___			12 + none
	G	2	L	12__5	NOGOOD		12 + 3rd-lowest
	R	2	L	12_4_	NOGOOD		12 + 2nd-lowest
	T	2	L	12_45			12 + 2nd-lowest + 3rd-lowest
	V	2	L	123__	NOGOOD		12 + lowest
							Use 12 + all binary combs of
							345 except "111" shd be enough
							for above group

	H	2	R	_2__5
	J	2	R	_2___
	M	2	R	_23__
	N	2	R	_23_5
	U	2	R	_2_4_
	Y	2	R	_2_45
							Use _2 + all binary combs of
							345 except "111" shd be enough
							for above group

	C	3	L	123__
	D	3	L	1_3__
	E	3	L	1_34_	NOGOOD

	I	3	R	__34_	NOGOOD
	K	3	R	__3__

	S	4	L	1_34_
	W	4	L	1__4_
	X	4	L	12_4_

	L	4	R	___4_
	O	4	R	__34_

	A	5	L	1_3_5
	Q	5	L	1___5
	Z	5	L	12__5

	P	5	R	__3_5

	sp	justthumb?
	lf	5	R
	.	4	R
	del-ch	
	del-wd	


--Rob