Half Frame Olympus Pen S. Get 72 frames out of a 36 exposure 35mm film roll.
Olympus used the Pen series, with the half-frame format, to jump-start the small camera revolution, replicating to some extent the philosophy that Kodak had in the early 1900s. Make something convenient and people will want to use it. These cameras were more popular than anyone ever expected.
So popular that Olympus has reintroduced the Pen name to its current range of crop sensor cameras, which coincidentally are Micro 4/3s and are exactly half-frame compared to a full-frame camera. It’s a pretty good bet that the brains at Olympus had made that connection. What is nice to see is that at least one of the major manufacturers of old, apart from Nikon and Canon, have survived and respect their history and heritage.