...Pretty late for a snap action under lever...
Possibly the customer went with what he knew? What his father had used, for example? "I'd like precisely what you supplied to my father fifteen years ago, which has rendered him wonderful service, except I need it to make larger holes."
Written in fountain pen, sent to the gunmakers via the Suez Canal. Lengthy back-and-forth correspondence ensues. Design is obsolete by the time it ships, but they still knew how to make 'em.