1942 over1 mercury dime

You make a valid point AG about the timing of when punched dates stopped. It's not that I was confused - just plain forgot. My explanation about the hand punched dates would apply to the older coins, but not the newer ones. I stand corrected on that score.

There is also a difference between a repunched date and an overdate, although both are obviously done intentionally. A repunched date is just like a repunched mint mark - it's the same date or mint mark but it is punched into the die twice for whatever reason. An overdate, or an over-mint mark, is two different dates or mint marks superimposed over one another. For example, an S/S mint mark is an RPM. But an S/D mint mark is an OMM. See what I mean ?

But the original point of the discussion was whether or not the '42/1 was an error or a variety. Well, the discussion of what constitutes an error and what constitutes a variety has been taking place for longer than I have been alive. And it's not likely that we are going to settle it here. I doubt it will ever be settled to be honest.

But you make good points, can't dispute that

To me it is quite simple - an error is something that was done by mistake. A variety is something that was done on purpose.