There were two MAB D versions, usually called the Type I and Type II. The Type I MAB D was made 1933-1945 and used an external muzzle bushing release latch in front of the trigger guard; the Type II used an internal "bayonet" type release requiring pushing in and turning the muzzle bushing. The MAB factory changed from Type I to Type II production in June 1945.
The MAB D pictured with this article is a Type I. The barrel release latch can be seen near the front of the frame in front of the trigger guard, as well as the Type I muzzle bushing.bushing.