Justin II and Sophia AE Half Follis 565-578 AD,
Obverse: DN IVSTINVS PP AVG, Justin left and Sophia right, seated facing on double-throne, both nimbate, Justin holding cross on globe, Sophia holding sceptre topped by cross
Reverse: Large K, ANNO, cross and regnal year
This is probably a reverse from a clashed die, i.e. the previously struck coin got stuck in the die holder and was used inadvertently as a die itself, that's why the entire reverse is back to front.