The oddest surprise I have found so far was in a 1969 Coronet 440.
The owner was leaving town and gave me the car for free. He had lost the trunk key years before when he was in college.
I got it open with one of the spare keys I have, there were pennies everywhere, over $22.00 worth.
The newest ones were dated 1969, the oldest was 1914.
No, I did not leave them in the car, I gave the old ones to a collector & took the rest to the bank.