Don, turret numbers are for visual control. American Army tanks since late 1940s have used a 2 digit system (until recently) and had 2 HQ tanks; 6 was CO, 5 was XO and 3 platoons of five numbering 1 thru 5. 1-2-3 were heavy section, 4-5 light section. 1 was platoon leader and 4 platoon sgt. 11 was 1st plat leader (2lt), 24 was 2nd plat sgt.. 35 was last tank in 3d plat light section. Prior to Pentomic, under the older regimental TO&E, an Inf regt had a company of tanks for support, with 4 platoons, so the 4th platoon was 41 to 45. Marking was white letters but Marines used yellow and often included the company letter.

Germany used a 3 digit system, first digit indicating the company, 2nd the platoon, and last digit the platoon number. ;ie 124 would be 1 Zug (kompanie), 2nd platoon, 4th tank. 1942-44 had zeros to indicate command...;301 = HQ co, one of the 2 HQ or command tanks. Later in the war, many modifications or alterations were made which completly confused the issue. So a tank commander of 2nd platoon could look over the field and see 133 and discern that it was his company but tank 3 of the 3d platoon. Other markings as R indicated a staff vehicle and often used Roman numerals as I or II...so RO1 was the regimental CO, but the system gets more complicated and wheh you get into SS units, the system is different to suit the SS needs. A Wehrmacht regt had 8 companies in 2 battalions, some later Tiger units had 9 and a few 10, which brings the 4 digit system into play.

British markings are a total "absolute secret" and I don't believe anyone knows the system.[:-]