Italian or prune plums are freestone plums, smaller and more oval than plums for eating out of hand. Prune plums are available in September where we live.
Wash waxy bloom from plums. Cut plums in half and remove the pits. Place plums in saucepan with water and sugar. Cover, and cook gently over low heat until soft, about 15 minutes.
Serve warm or cold with cream.
Beverly Pepper, The Glamour Magazine After Five Cookbook, 1952 (modified)
http://macheads2.net/recipes/StewedPlums.html