yea they are not that rare, but are interesting.
I actually bought something in japan in an antiques shop, that is used as something (coins tied together with some stip of paper dangling down) and it was interesting in the fact it had coins dating from the 1100s on up to the 1760's wave cash
the 1100's 10 cash is large as well, but mainly worth.. not a lot.
I also own one of the 50 cash
for size, its about the size of the cartwheel twopence
whats great about Chinese coins are you can get really old coins.. for next to nothing.