Each section of the process was overseen by one of the prisoners, and the day-to-day operations were run by Oscar Stein,[n 7] a former office manager and bookkeeper.[51] Two twelve-hour shifts ensured non-stop production, with around 140 prisoners working.[n 8] The printed sheets, each containing four notes, were dried and cropped using a steel ruler; the edges were roughened to imitate the deckle finish of the British notes.[n 9] The operation peaked between mid-1943 and mid-1944, with approximately 65,000 notes a month produced from six flat-bed printing presses.[53]