Due to abuses by offshore and U.S. based gray market counterfeiters, the U.S. government has imposed a new marking standard for MS part numbers. Legitimate franchised and approved sources are now marking MIL-STD-5015 connectors with a J prefix. The MS prefix was never copyrighted and was being duplicated by unscrupulous counterfeiters. The U.S. government has now protected the JMS call out – just as they had previously done for the older JAN call out. So if you order, for example, an MS3106F10SL-3P connector, the connector itself will come marked JMS3106F10SL-3P signifying that it is an authentic mil-spec part.
If your supplier is shipping you old MS nomenclature parts, beware of your source of supply. Approved military marking should now include the J or JAN prefix.