The following images are of a .450 (45 Short) CS gas blank by/for Helmut Diehl, and an 8mm gas blank by Hirtenberger. Both have “SM” on the headstamp. I have been told that “SM” stands for “Schusswaffen und Munition” but I do not understand the context. Is “Schusswaffen und Munition” the name of a company or a reference to European legislation governing the use of CS blanks (both have been suggested to me), or is there a third explanation?
(I do not collect gas blanks, per se, unless they are .450/.45 Short. I have included the image of the 8mm to show that “SM” is used on gas blanks of different calibers and manufacturers.)