These are so cool! It's amazing how affordable some of these are, even if they date back a thousand years or so!
There is one annual coin show I like to attend, and one vendor has these. I have to bring a binder with what I've already got, just to make sure I don't pick up duplicates.
Then, there's the matter of finding ones from other countries that made them like this. Japan, Korea, Vietnam...Unless you have references, it's easy to get confused.