Bob:
Interesting story. I don't know how widespread this "last man" practice is but the Vet that lived across the street from me when I was still in Illinois told me his unit had done this very same thing.
Jim

Very cool story Bob, thanks for posting.

Things of this nature are called 'tontines'.
The survivors of the Doolittle Tokyo Raid in 1942 also have an agreement with the drink being a bottle of champagne.