I would imagine that the spring would have had to be pretty strong to prevent just that kind of accident. Still, it is like inventing the square wheel (can't accidentally roll away!) because one is tired of looking at round ones. I guess the "trigger guard" was just to satisfy convention.
The value on something like that is always debatable. It is certainly rare; there are probably more Paterson Colts around. Yet, it was a design dead end, not the beginning of a legendary company. Any WAGs? I would say maybe $400 to an auto pistol collector.