What I was trying to say was:
1. Person puts 2 (or more) pennies aside at the time they were issued. These would be strikes from the same die if got from a bank.
2. The pennies stay in the same family for generations.
3. In modern times the current owners decide to sell, which means two pennies struck within minutes of each other, appear on the market in a relatively short space of time, complete with identical die flaws.