Everyone else on this thread has concentrated on the split adjusted vs actual cost on some date in 1996. Is it possible that you have access to your father's bank/credit union/? records? I know many people keep cancelled checks for years. Can you find out how much your father paid into the defunct brokerage firm and when? This may give you a clue as to the cost and when the stock was purchased.

Also, did an existing brokerage buy the defunct brokerage? Can they research the old records?

It also seems quite possible to me that the cost basis that your father wrote back in 1996 had nothing to do with the date 9/24/96. That cost number is associated with the purchase date, which you don't know, but, it is before 9/24/96.

Good Luck

Terry