I would say the 1970's and early 1980's... but they can occur on all years on all denominations. I don't think there is an actual survey or record kept of when MAD issues happened the most.
I would agree with that. A lot of things seemed to deteriorate significantly starting in the early 70's, and not getting better til the mid 80's, not just coins. But yeah, mint quality was horrible during this timeframe.
as stated, all years/all denominations... and from what i've seen, not really considered a collectable error, as they are just so common, if you roll search, you can easily acquire hundreds very quickly..
Extreme MAD is collectible, but I think they call those "off center", unless I am mistaken and are produced differently. My understanding for "off center" is that the coin is struck before it has seated fully in the collar, whereas the MAD is fully seated but the die/collar adjustment is out of adjustment. Spark
Agree with Paddy also. You just may have hit a few 82's with MADs. Off center are misaligned on both sides. MAD on just one side and the other side is centered correctly.
I like them all. Your questions really a stretch. I'm going to say every year the day after St. Patty's Day of every year is my guess
MAD's can be off on both sides, in the same or different directions. But the Anvil die can never be off by much because it is restrained within the collar.