1980 LMC-Nice Example Of MD On The Date

Everything else is normal. Only affects the date.

Dipped and sealed.

Excellent example! This is (will be) good to show to noobs. Note that the statement "MD reduces the size of the devices" is ambiguous here, VERY hard for the untrained to distinguish because there is little Size reduction. Why here when we see the shelving effect so distinctly? This is a "Push Doubling" effect. Normally the die hops up and comes back down fairly straight. Here on the upstroke it grabbed the edge and pushed the metal before settling down. This is what does indeed cause confusion when first learning how to recognize these buggers!

DD is more rare as the dies that struck the coins had design doubling of some sort. MD is caused by extraneous movement of the die and can happen with any die.

Another noob in the area of Mechanical Doubling (MD) with questions. I have researched this topic, and the available information seems to be limited to (1) descriptions of what MD is and how it occurs, and (2) that it is generally not considered collectable by most numismatists. Given that the process of creating coins with MD is fairly understood, I am curious if anyone can provide more specific details (if known) to help educate novices about MD in general and why its relation to a coin's value as opposed to Doubled Dies and other types of errors is so lowly considered.
(I hope I have not exceeded the limit for the number of questions for one post!)

How long does it take mint employees to correct a MD problem once discovered? (Or do they bother?)
How long is a DD used once discovered?
Are there examples of DD coins also having MD?
Is it possible to have a run of coins with a pair of dies that never produce MD?
If a coin does receive MD, does this mean that all or nearly all subsequent coins struck in the same run (i.e., same press, same dies, same collar, etc.) will also have MD, or is it possible that only a single coin (or just a few) in the run could receive MD?
If there are multiple cases of MD in a particular run, is the doubling identical on each affected coin, or can the doubling be random from coin to coin due to the mechanical variables?
It seems that the idealized objective of minting coins is to stamp out "perfect" specimens, so why is MD (which is unintentional and produces non-perfect specimens) not considered as desirable as DD specimens - which result in continuous, identical, imperfect specimens (until discovered and the dies are replaced) and are the result of human error?
Why is MD not considered equivalent, value-wise, to other mechanical-related errors (such as off-center strikes, double strikes, major die cracks, die clashes, Cuds, etc.)? Mechanical is Mechanical, right?

(Ok - last one: Is a die crack a mechanical "error" or damage?)

In the long run, it's a matter of collector appeal; I am intrigued by MD coins, but if there's no increase of a coin's value, it's hard to justify not just dropping it into a piggy bank for future spending. Seems a shame. Anyway, many thanks for the patience of anyone who decides to take on these questions; I feel that every little bit of education can help a lot of new collectors (young & older).

Thanks Coop! I totally agree - knowing the full story is so much better than a single sentence answer, which may or may not give the questioner all the information desired. This forum is awesome, and it is refreshing to find so many people who are willing to share their knowledge and experience with new-comers.