What does the "M" in M252 stand for in military nomenclature?

In military nomenclature, the "M" in M252 stands for "Model." This designation indicates the specific version or type of equipment within a series of military items. For example, the M252 is a particular model of an 81mm mortar system used by various armed forces. Understanding this nomenclature is critical for proper identification of equipment and ensuring effective communication among military personnel. The use of "Model" signifies that this mortar is one in a sequential system of designations, distinguishing it from other models that may serve different purposes or possess different features.