Jon Speed's book, The Mauser Archive, refers to this kind of set trigger as "recurved" and it was the type of trigger installed as far as I know on all Mauser sporters other than the very early ones. The cut-off date appears to be World War I. On page 530 there are photographs of two rifles, both made in 1922-23. One has the recurve trigger, the other does not. Speed comments, "Note the first appearance in this chapter of the distinctive recurve on the front trigger, adopted after WWI."

All of the ones in my possession are so equipped, including two Model S carbines and four Type B sporters.