I have a Casio MT-205 that I'm bending, that I'd ultimately like to try to sync with a Casio MT-520 by connecting clock output of one crystal to the input on the other. On the crystal, how can I tell which leg is output and which one is in? Any other advice in tackling this project? Thanks!
I think you might have misunderstood something somewhere along the way.
Theres no such concept as 'connecting clock output of one crystal to the input on the other'
What exactly are you actually trying to do, and why do you think that doing this might achieve it?
do you mean something like this?
http://casperelectronics.com/finished-pieces/casio-mt-240/