What does the M stand for when it's at the end of a serial number when dealing in Norinco SKS?

In the context of Norinco SKS rifles, the "M" at the end of a serial number typically indicates that the firearm is a variant known as the SKS-M. This model features specific modifications, such as the ability to accept detachable magazines, distinguishing it from the standard SKS models. The "M" designation helps collectors and enthusiasts identify the specific configuration and features of the rifle.