CoinWeek reports on a rare find by a NGC coin grader who was working through a bulk submission of nearly 1,000 Morgan Dollars. As you can see from the photo on left, the die that made this San Francisco-minted 1921 Morgan had the mintmark almost totally filled with grease when it struck this coin. Estimates of the value of this coin is nearly $1000.
I'd have never seen that, myself. That's why they get paid the big bucks and I don't!