Those are magnificent coins! The three-sisters coin is a treasure, as are the others. I'm seriously impressed!
This is a particularly nice example of this sestertius. Congratulations! I've always thought that Caligula's portraits on his denarii and aurei looked more demented and angrier than his AE portraits:
Caligula, Roman Empire, As, 37–38 AD, Rome mint. Obv: C CAESAR GERMANICVS PON M TR POT, bare-headed head left. Rev: VESTA, Vesta seated left holding patera and sceptre. S–C. 28 mm, 10.18 g. Ref: RIC I, 38. Ex Spartan.