Ringo, the Mark of Vengeance (1966)

Story of two friends who rescue bumbling bandit Fidel from a shootout. While patching him up, they discover half of a treasure map tattooed on his back. Learning that the other half is tattooed on the back of someone else, they set about trying to put the two halves together while being joined by card sharp and all round trickster who discovers their secret and wants in on the deal.