What were first da/sa and double stack guns?

[Nyles]

Well, the Savage 1907 pistol had not QUITE a double-stack mag, but it was staggered dual column, and they were quite popular at one point. Used in pretty large numbers by the Portugese military in WW1, and smaller numbers by the French.

The Roth-Steyr 1907 uses a very similar trigger to the Glock where the striker is partially cocked when the bolt closes, and the trigger then fully cocks and releases it. I guess you could argue that the Webley-Fosberry used a DA/SA trigger, but that gun is kind of in a class all its own.