Pop-pop boats come in a wide variety of shapes and sizes, but they are mostly cheap toys in the classical sense. Most available today are modern reproductions of toys made 50-100 years ago. Very few of the originals survive. This example is the only one I have not branded Rattandeep.
The "works" consist of a small chamber from which lead two parallel pipes terminating at the stern end under the waterline. And that's it!
The heat source can be almost any source of flame small enough to fit under the chamber. With the boat when purchased was a tiny candle in a small spoon shaped device. There is no rudder so it can only go in (roughly) straight lines. It is, therefore, not suitable for large expanses of deep water!
Construction is entirely pressed "tin-plate" and is painted all over in a rather nice metalic blue.