The Walther MP was an all-stamped submachine gun developed in the late 1950s, and available in long (MPL) and short (MPK) versions. It is an open-bolt, blowback design, but uses a somewhat innovative bolt in which most of the mass is located above and in front of the chamber, to reduce bolt travel and receiver length. I found it to be a very pleasant gun to shoot, and I suspect it was largely unsuccessful in large part due to the superior marketing skills of H&K with their MP5 submachine gun.