It occurs to me that the coins I'm thinking of all date to the Middle Ages and prior. I only ever collected US coins, and my books seem to show that by the 1600's mints were starting to get a handle on the centering issue, and coins minted in the 1700's are only a little more wobbly than they are today. That's the run-up to the Industrial Revolution. As children of the machine age, we're all used to precision as a matter of course — even when it doesn't really matter, our artifacts are precise just because it's easier that way. To the people who were making and using these early coins which so often lose part of the design off the planchet, it may not have mattered, as long as you could tell what it was.