The suave daring super thief was epitomized in MARIO BAVA's classic DANGER DIABOLIK, but DIABOLIK definitely borrowed big time from this flick...
MISTER X, a mysterious thief and master of disguise and his ever lovely cohort, who steal more for the thrill than the having, are brought out of retirement to clear MISTER X's name. A evil crime lord has killed his girlfriend (who knew too much) and has pinned the rap on MISTER X. MISTER X becomes AVENGER X as he takes on the crime syndicate.
Sure this didn't have the budget of DIABOLIK but it has lots of that '60s James Bond type super-spy type action. AVENGER X takes on various disguises, uses all sorts of nifty gadgets and there are plenty of fights and gunplay and danger and seduction as both the criminals and the cops get him in the squeeze play.
Definitely a flick ahead of it's day....