If you know much about pistols there shouldn’t be much mystery to this. At least, you could hazard a guess on how they’re fired. The man who owned them was Manuel Trazazas “Lone Wolf” Gonzaullas. He was a lifelong Texas Ranger and is notable for being the first Hispanic ranger to rise to the rank of captain. He started his career back in 1920.
Back then he combated bootlegging, bank robberies, narcotics trafficking, and prostitution. Later in life, he also helped to establish one of the best crime labs in the country at the Texas Department of Public Safety. Eventually, he retired and became a technical advisor in Hollywood.
He owned many different kinds of guns throughout his life that were all engraved with his name, including a pair of revolvers that didn’t have triggers. They were fired by cocking and releasing the hammers.