Constantine I AE Follis. 

Obv: CONSTAN-TINVS AVG, helmeted, cuirassed bust right 
Rev: BEATA TRAN-QVILLITAS, Globe on an altar, altar is inscribed 
  VO / TIS / XX in three lines, three stars above; 
Mintmark: PTR. 

RIC VII Trier 316, rated R3

Contributed by Dane for George Clegg (biggyg2), October 2007