I looked through the historic iris society webpage and noted a few possibilities. But none mention fragrance---not usually something that was included in descriptions at that time. Might not have been a registered iris. This person might be happy with Oasis Root Beer if it is the fragrance that evokes the memories.
(note: some of these may be more reddish than brown):
Tobacco Road
Tabasco 1950s intro--quite pretty actually
Spanish Lady
Royal Scot
Good luck!
