I don't have a broker, I bought this fund directly from Oakmark. And I only keep tax records back 7 years so I don't have any access to early transactions.
Oakmark wants me to select my choice of Cost Basis Method. Their choices are:
Average Cost
First In, First Out
High Cost, First Out
Last In, First Out
Loss/Gain Utilization
Low Cost, First Out
Specific Lot Identification
I guess I'll have to select Average Cost and pay the price for not keeping detailed records.