I wonder if it might be a bit of a mix of MD over
DDD, you should hang onto it for reference. I had a lot of trouble with doubled dies when I started and as you see more examples of all forms of doubling they start to just stand out to you(at least in most cases) I have seen a few examples of doubled dies that were flattened by MD, idk how hard it would be if I saw a doubled die with
DDD and MD to be able to tell of it was a doubled die.
Practice and study make perfect(or at least better lol) in a hobby like this there is truely no such thing as perfection imho, even the most seasoned experts learn new things every now and then(I'm far from a seasoned expert).