I agree it MD. I may be wrong which I usually am. But I have found if there is doubling on multiple devices especially the bust then it's almost always MD. But keep looking and you'll find it eventually!
Like Mark said, MD looks shelf like-flat, like part of the lettering was pressed flat. DD is 'part' of the lettering. Usually level or almost level to the lettering height. It looks like additional material to the normal devices-usually (but not always) tilted/skewed/lowered or raised from the lettering to create a 'notch.'
Coming across MD a lot will train your brain to recognize it more and more. Eventually when you do find a DD, it'll look drastically different to your MD trained eye.
Comparing your coin to actual listed DDOs and DDRs as a guide is a great practice. Check out doubleddie.com, CONECA master listings, and variety vista (to name just a few).
Keep up the hunt! Always post to the forums-when in doubt let the forums check it out!