Old King of Bel Air (1951 B.C.)
The car the vet drives. Or doesn't, nobody has seen him leave his house since Vietnam.
It's in immaculate condition though and that's why Todd thought it'd be funny to key it. 365 times. No, not over a year, but over 20 minutes until his key got worn out and he could not use it.
That's the reason he forgot what it was for, since he couldn't check a lock with it anymore.
Rumors are that the key was to be used in a mission for a top secret bank heist.