Trebonianus Gallus. Like this one: Trebonianus Gallus, AD 251-253. Roman AR antoninianus, 3.60 g, 19.2 mm, 6h. Rome, 6th officina, 4th emission, early AD 253. Obv: IMP CAE C VIB TREB GALLVS AVG, radiate, draped and cuirassed bust, right. Rev: APOLL SALVTARI, Apollo standing left, holding branch with right hand and resting left hand on lyre set on rock. Refs: RIC 32; Cohen/RSC 20; RCV 9627; Hunter 21.
Yep, it's TG. Gallienus' coinage started out okay but quickly degraded with the debasement and poor design of the coins from the rest of his reign. The Empire was being pulled apart by the seams at the time, including an economic crisis that led to jillions of poor quality low value coins that probably had very little purchasing power.
Bojan, May I suggest a book for your library: ANCIENT COIN COLLECTING III, The Roman World - Politics and Propaganda by Wayne Sayles. This is an excellent book for beginners interested in Roman coins & pictures coins of each Roman emperor along with relevant information. Used copies sell for as little as $10.
