encoder

Some may remember me asking about electronics merit badge about 3
weeks ago. We had a good evening and will have more, but night turned
out to be more of intro to electronics rather than all the work for a
merit badge. We did some soldering/desoldering, took apart several
old mice and an inkjet printer, built a couple simple circuits with
Radio Shack 300 in 1 kits and played a little with a VEX robot.

Have a couple kids interested in continuing.

My questions - I've been looking for quadrature encoders to learn
about and use for DRO on school mill etc. I presumed that the black
plastic wheel encoders we've taken out of copy machines and now mice
have not been quadrature, and that MAYBE some of the are clear disks
and the long plastic tape with very small lines might be quadrature,
but after thinking about it, might the mice ones be quadrature - and
if not, how can they tell which way my hand is moving?? And ques 2 -
how do we tell if the printer stuff is quadrature or not?? thanks in
advance, Chuck