Expert on these, I am not. But, my 360J is clearly marked .38Spec on the barrel and on the box. May have been mentioned above, but my understanding is the "J" comes from an order from the Japanese national police. Either way - it's a keeper! I found mine used locally - and I am trying to save my SBUX money for one the five new ones currently listed on GB. I will have to sell a 442 to fund it but I like the 360J that much ...