I think there are about seven or eight marks of that design, but I've never been able to find out anything about what the changes were. The fact that it seems almost impossible to pin down exactly what mark any given DR actually is has probably contributed to it's popularity. Add to that the "Duck Rule" and it truly is a very "flexible" design. I'm not suggesting that's not a good thing. Though, I honestly never found the MAN version to have any visual appeal. I can't even award it the "form follows function" caveat.