The best way to tell is on the curved devices. MD alters these in a straight line:
Note how the left image is showing strong
Machine Doubling on the Lower SW on the left image?


I mention often the reduction of the devices. But seeing them side by side shows how this reduction really shows:

So look at the curved devices. This will show the reduction from the normal size of the devices will be altered:


Also note that the MD always affects the outside edge of the devices.
On the doubled dies you will see a spread line on the centers of them and the edge are untouched except for notching marks.