Brand name for a
kerosene pressure lantern.
First sold in Germany in 1910 by it's inventor, Max Graetz, it was originally built locally.
Nowadays, most of those lanterns are built in China, under license by the German company still holding the rights to the name.
The design has undergone minor changes, but the changes were very minor, especially after the 1950s. Still - if you buy one today, i.e. a Petromax 500 CP, it will still be outfitted with a leather-sealed pump.
The Petromax is still very much in favour with the German Bundeswehr - also a number of emergency services use them as a very bright light source in places lacking electricity.
The light produced by the top model, the above-mentioned 500 CP is deemed to be equivalent to a 400 watt light bulb.
Operation and startup take both skill and effort.
After installing a mantle and burning it (yes, literally, the remaining ashes contain substances that glow under te influence of heat and are brittle, yet stable enough to withstand the fire burning inside it), you build up pressure in the kerosene tank by using a little leather-sealed pump.
Then, you pull a tiny lever to start the quick heating device, which will shoot a spray of kerosene up the innards of the lamp.
You ignite the spray and let the lantern heat up for 90 seconds, keeping up the pressure by pumping at the same time.
After the heat-up phase, you open the carburator main valve while closing the quick heating device at the same time. If you are skillful or lucky enough, the lamp will now start to emit a bright, white light, requiring little, if any, additional pumping work. One liter of kerosene will last for approximately 8 hours.