[Paul]

Filip,

Ken had some time to check things:

Both 21-A and 21-B were allocated to the Artillery HQ Air Section of the 8th Armored Division. The three Armored Field Artillery Battalions of the 8th Armd Div received 'squadron code markings' as follows: 21-C and -D went to the 398th Armd FA Bn; 21-E and -F to the 399th Armd FA Bn; and -G and -H to the 405th Armd FA Bn. Unlike Armored Divisions, which had eight aircraft shared between three Armd FA Bns and a Div Arty HQ, Infantry and Airborne Divs had four Battalions and therefore received ten aircraft, lettered A to K ('I' was not used to avoid possible confusion with the number '1'). This number/letter unit code system was used by the Armies of 12th Army Group (First, Third, Ninth and Fifteenth US Armies). A different system, employing two letters only, was used for unit identification in Italy and elsewhere in Southern and Central Europe by the Fifth and Seventh US Armies. This system did not provide for individual aircraft identification, the two or more aircraft of a battalion or other unit carrying the same two-letter code.

Filip, if you have more questions please ask.