Some of the methods inside the Economy_CurrencyCore class in the version you released are faulty.
bankBalance creates a bank instead of returning the balance, while the outputs of methods like bankWithdraw and withdrawPlayer which do the same thing, are inconsistent.
This really does put a hole in the usability of CurrencyCore.

sorry had some bugs. Would have been better if you had done a pull request onto the repo with the original code. but I'll get it fixed

err, the bank/playerWithdraw methods are identical except for minor formatting.

fixed the bankBalance method. looked like I copy/pasted it from the createBank and never altered it properly.