 The trigger became visible only upon cocking the hammer.A subsequent patent renewal in 1849, and aggressive litigation against infringements, gave Colt a domestic monopoly on revolver development until the middle 1850s.Early Colt literature and later publications insist that Colt was inspired to design the revolver in 1830 by viewing the windlass mechanisms aboard the brig "Corvo" while bound from Boston to Calcutta.