c. 32 BBY
While taking the final test, Bravo Squad was the first to take the Citadel Challenge and complete it. They then became troopers of the Grand Army of the Republic and were stationed somewhere. CT-66-3232 was one of the troopers with the number 2 on his armor.
This Bravo Squad cadet's identification number was first depicted in the picture to the left. It says 66-3232. And the prefix was known to be CT, as all clone cadets have CT numbers. This way of determining identification numbers was proved with the troopers in Domino Squad.