OPA Tokens

I found the following statement online concerning the check codes on OPA tokens.

The check letters when charted form a nice little rectangle and their layout forms a definite pattern with the exception of the MM and the MV.

What exactly does this mean, when charted? I cannot figure it out.

Thanks for any help with this.

I found the statement here: https://forums.collectors.com/discussion/443870/opa-tokens

I'm to lazy to try it, but I suspect if you made a 26x26 grid labeled by letters and put an X where the row letter matched the first letter on a token and the column letter matched the second letter you would see a pattern in the result.

I expect someone will be more ambitious than I am and post the result of this test soon.

The two OPA tokens I can find on Numista (with letter combinations listed):
https://en.numista.com/catalogue/pieces21179.html
https://en.numista.com/catalogue/pieces42308.html

I did the 26X26 grid. I did not see a nice little rectangle nor a definite pattern. Then I got frustrated and deleted it. I'll redo it and post here. Maybe somebody else will see something I missed.

I think the pattern is that only certain letters were used, and almost all combinations of those letters were used.
(Except for M.)