Quote: Many of the letters and the top of her crown are re-stamped (proper term?)
I think you're referring to the doubling. This is Machine Doubling and very common. It isn't a variety, just the die juddered a bit when it hit the coin.
Double dies are the other possibility, where the doubling is on the die and so lots of coins have the same doubling - these are varieties (because lots of coins will have it) but as has been said, unlike US coins, British double die coins don't tend to go for huge money.