This may have been discussed before but the presence of the Mauser hump on K date lugers is a fascinating subject. They appear to be solely at random. Does anyone know if Mauser ran several pieces consectively with the hump? Why do some have it and some don't? Was it a maverick experiment that one production line ran? The hump disappears until sometime in the late 1937 year and seem to become a constant feature after the "t" suffix when all parts were blued. The reason for the hump was to prevent falling out of the rear toggle pin with the weapon in full recoil. Why did some workers apparently get this message, find it a good idea and others not in 1934? This is just another feature that makes "K" dates fascinating.