RT-42/7621

RT-42/7621 known as Marx was a marksmen from the 42nd Attack Squad. He was called the Clone Trooper of the Squad.

Cloning
RT-42/7621 was cloned 10 years before the Sith Extinction War, it is unknown who was the person he was cloned after.

Military training
Marx was on growth acceration for 10 years for his training. when he was physicaly 20 years old; he was then allowed to age normally.