Constantius II AE2. 330-355 AD D N CONSTANTIVS P F AVG, diademed, draped and cuirassed bust left, holding globe / FEL TEMP REPARATIO, emperor standing left holding chi-rho banner and resting hand on shield, 2 captives standing to left. Mintmark CONSH.
One of the less common FEL TEMP types. The chi-rho in the standard (which is why the standard is called a laborum in many descriptions) is a fairly early example of Christian imagery on a coin, which makes it very interesting to some collectors. BTW, Constantius II reigned as co-emperor or emperor from 337-361 A.D. Your coin was minted between 348-351 A.D.
Also: When issued, this coin was the middle of a set of three denominations (perhaps half or one and double the other). Various mints preferred different reverses but the middle denamination had the bust left separating it easily from the smaller and larger with their right facing portraits. Before long, inflation ended the two smaller coins and the largest one (the Falling Horseman) shrank again and again until it was much smaller than the original small size (Phoenix reverse) coins. Along the way, the coin below was overstruck converting it from the smaller denomination like your coin to a then current falling horseman of that size. The left bust and feet of the captives can be seen when the coin is rotated as in the upper set below.
