There are also square front smooth bottom mags (no Banner). The square front banner you show also has cliped corners which I believe is correct for late 1914s and early 1914/34 transitionals. Penders information is not complete for magazines. John LeCroix published an article in AutoMag on Mauser pocket pistol mags but I do not think it was conclusive. He was in the process of gathering data. This is an area of reseach that I have a interest in but I do not have enough data to provide much more that you already know. Hope this is helpful to you!
NRA life member, NAPCA member
Aim small, miss small.