I know it was a long time ago, but did her family keep any of his rifles? If not maybe the family kept information on file for selling them for any reason? As nitestalker said, stocks are built around your action, so most likely he was probably making a stock for one of his rifles. Ask the family if you didnt already. Id say a .22lr maybe browning or remington?
"There was a time when the world asked ordinary men to do extraordinary things."