The Spes Publica type, showing a labarum piercing a serpent and minted only in Constantinople in 326, may be a purely Christian design. (Kenneth Jacob, author of Coins and Christianity, in a letter to the author dated Feb. 14, 1985.) But this is debated. Patrick Bruun, for one, is skeptical. See Bruun, Roman Imperial Coinage, Vol. 7, p. 61 ff. The argument centers on whether the serpent represents the biblical Satan or simply a universal symbol of evil. Since the concept of defeating a great evil that threatened the empire had been depicted thus in coinage for centuries, the design is too ambiguous to make either interpretation certain.