In the 2009 anime, Fullmetal Alchemist: Brotherhood, near the end of the series,
Scar fights Wrath. During the battle, Scar surprises Wrath by using construction alchemy, revealing that he has a construction-based tattoo on his left arm.
Scar has not had this tattoo forever, though; in earlier scenes in the series, we can clearly see that Scar has only one tattoo on his body.
Is it ever stated when Scar receives this tattoo? Who gave it to him?