Olympus Trip 35

The Pen is a half-frame film camera that uses 35mm film. The first-generation Olympus Pen camera appeared in 1959. 

a film camera that uses a film format that's half the size of a standard 35mm film frame. This means that each exposure is half the size of a standard frame, resulting in a smaller image size.

for example if you place a 36exp film you will be able to take 72 photos instead of 36 photos!