MD is considered worthless doubling.. It has absolutely nothing to do with a true Doubled Die. Whatever the coin denomination is.. That's what it's worth. And.. I don't consider Mechanical Doubling an error nor variety
Here is some information http://doubleddie.com/144801.html Look at the rest of that website to understand what the differences are.
The only good mechanical doubling serves is to teach newbies the difference between that and true hub doubling.
MD is fun and exciting to find and look at for us rookies but after awhile it fades and you only keep extreme examples.
I would not pay a premium for a coin with machine doubling as I would with doubled dies but I do not view machine doubling as damaged since it occurs at the mint.