Matchless (1967)

“THIS WOMAN is the most thrilling act of espionage you've ever seen! She holds the key to "Matchless" - a spy plot as flawless as her beauty - as reckless as her body!”

A secret agent possesses a ring that makes him invisible for a short time, once every 10 hours. He is in pursuit of an evil criminal mastermind but, at the same time, must evade an enemy agent who also wants the ring.