These seem to be common enough, but yours is in excellent condition. Looks like a nice thick dark patina.
Here's mine from Philip I: Philip I, AD 244-248 AE, 15.1g, 28mm; 6h; Viminacium, AD 248 Obv.: IMP M IVL PHILIPPVS AVG; laureate, draped, & cuirassed bust right Rev.: P M S COL VIM; Moesia standing, looking left between bull and lion In Ex.: AN VIIII
My only Viminacium, which came in the mail from Frank Robinson just today! Herennia Etruscilla, AD 149-151 Roman provincial AE 27 Moesia Superior, Viminacium, AD 149-150 12.67 g; 27.45 mm; 07:00 Obv: HER ETRVSCILLA AVG, diademed and draped bust, r. on crescent. Rev: PMS COL VIM, Moesia standing facing, head l., between bull standing r. and lion l.; in exergue: ANXI (year 11=AD 249/50) Refs: Pick 136; Moushmov 48; SGI 4220 var.; BMC 3. 18, 32 var.
Here is a Gordian III of Viminacium struck "ANIIII" = year 4 = 242/3 AD. 28 mm. 21.24 grams. IMP GORDIANVS PIVS FEL AVG (a Regular Latin legend, not Greek) PMS C O L VIM Female standing holding vexilla inscribed "VII" with bull below and "IIII" with lion below for legions 7 (Claudia Pia Fidelis) and 4 (Flavia). After I bought this in 1995 I studied up on Provincial coins with numbered legions mentioned on them. There are not very many and a theme collection would not be large. However, they are infrequently offered. If you want to collect ancient coins, you would have to collect some other theme too while you were are waiting for numbered-legion types to appear.
Cool! I have a couple from V-town! RI Hostilian 251 CE AE 27 Viminacium Moesia Bull-Lion RI Aemilianus 253 CE AE24 Viminacium mint Moesia Bull-Lion - Damnatio Memoriae