I’m not a Marlin expert by any means and I don’t have in depth knowledge of the JM stamp. I believe Marlins before Remington owned Marlin or at least the 336 Marlins had the JM stamp. I don’t think the JM stamp is on Marlins produced during the Remington years and of course not during the current Ruger Production. A guy can Google more about the JM stamp and learn far more in short order than I can share. I just know a lot of die hard Marlin guys look for that JM stamp. I own a few of the older Jm stamped rifles and really like them.I understand and appreciate you wanting to help me. Isnt JM just the fact that it's actually a marlin? This gun is going on 70 years old. If people don't realize it's an actual marlin and has a stamp, they shouldn't own it lol