I make simple springs like this (obviously not for locks or other critical function) out of brass all the time. It's remarkable how 'springy' a piece of brass that is repetitively hammer-hardened will be, and provided the range of motion required is not much (as in this case) they seem to last just as long as steel.
The catch looks to be steel, however - how is it attached to the brass spring? I'm going to assume that there is a tit on the backside of the catch that goes through a hole in the brass and is riveted. I think solder might be on the weaker side, unless it was silver soldered.