There were about 11,000 of the .38-44 Heavy Duty revolvers made. The 5" inch barrels were the most common (like the one I have). I think there appears to be more out there because of places like Gunbroker where you get to see a bunch at one time.
Great revolver. I have one of the pre-war 5" versions. Congratulations. For many years the Heavy Duty was a great bargain, but that was a long time ago. They're now appreciated.