Constantinople, Ca. AD 913-959
Constantine VII with Romanus I and Christ Av. solidus, Constantinople. +IhS XPS REX REGNANTIUM*; Christ nimbate, seated facing, raising right hand in benediction and holding book of gospel. Rev. ROMAn ET XPISTOFO’ AUGG b; facing busts of Romanus I with short beard and loros, on left, and Christ, beardless, with chlamys, on right, both crowned and holding long patriarchal cross between them. DO 7; Sear 1745. 

Constantine VII, son of Leo VI and his fourth wife Zoe, enjoyed an unusually long reign that was often dominated by co-regents. Romanus I was one such ruler, reigning from AD 919-944 before being deposed by his two sons, Stephen and Constantine.

The image of Christ did not appear on Byzantine coinage until the end of the 7th Century AD, under Justinian II. This reverse represents an expansion of this theme, depicting Christ seated with the inscription “rex regnantium” (“king of those who rule”). This was intended to promote the idea that God used the emperor as his representative on earth, ruling through him as a divine instrument.

For additional information see:
Wroth, W., 1908, Catalogue of the Imperial Byzantine Coins in the British Museum. London