Explanation of 'J' and 'JAN' Marking

'J' & 'JAN' Marking on Mil-Spec Connectors
DFARS stands for "Defense Federal Acquisition Regulations Supplement".
j marking connector
What is DFARS?
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. Franchised and approved sources are now marking MIL-STD 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. For example, if you order a MS3470L14-5PX connector, the connector itself will come marked JMS3470L14-5PX signifying that it is an authentic mil-spec part.
Excerpt from MIL-DTL-5015H
*3.30.3 JAN Brand
The United States Government has adopted, and is exercising legitimate control over the certification marks, "JAN" and "J", respectively, to indicate that items so marked or identified are manufactured to, and meet all the requirements of specifications. Accordingly, items acquired to, and meeting all the criteria specified herein and in applicable specifications shall bear the certification mark "JAN" except that items too small to bear the certification mark "JAN" shall bear the letter "J". The "JAN" or "J" shall be placed immediately before the part number except that if such location would place a hardship on the manufacturer in connection with such marking, the "JAN" or "J" may be located on the first line above or below the part number. Items furnished under contracts or orders which either permit or require deviation from the conditions or requirements specified herein or in applicable specifications shall not bear "JAN" or "J". In the event an item fails to meet the requirements of this specification and the applicable specification sheets or associated specifications, the manufacturer shall remove completely the military part number and the "JAN" or "J" from the sample tested and also from all items represented by the sample. The "JAN" or "J" certification mark shall not be used on products acquired to contractor drawings or specifications. The United States Government has obtained Certificate and Registration Number 504,860 for the certification mark "JAN" and Registration Number 1,586,261 for the certification mark “J”