How about money counting machines? Medium and bigger shops probably have those and if not they probably at least every few days bring cash to bank to deposit on

How about money counting machines? Medium and bigger shops probably have those and if not they probably at least every few days bring cash to bank to deposit on their account. Remember supposedly most printers were printing some semi invisible serial codes - for tracking whistleblowers and leaks. Probably cannot easily prove that ATM or money counter machines manufactures are not doing something similar.