6. Although the BoP had been structured after the great-grandmother of all central banks, the Bank of England, there were key omissions in their standard operating procedures. When a note, no matter how little worn, was returned to the Bank of England the serial number was noted and the note retired from further use and a new one would be issued in its place. However, the BoP saw the costs of eliminating dirty money using the British methods as an unnecessary expense and so instead of recording serial numbers or removing damaged bills from circulation, currency was washed and left to circulate until it essentially disintegrated into dust.