This paraffin gas burner was manufactured in the early to mid 20th century by the Valor company, and was designed both to warm a space, and to be a cooking stove. It is made predominently of metal, in this case painted green, and consists of: a reservoir at the base, into which the paraffin could be poured through a hinged stopper; a chimney which housed the wick, with a hinged glass window allowing access to light or trim the wick; and a flat, round surface on the top with ribs to support a kettle or saucepan for heating.
Items such as this were popular in the early 20th century were popular as they were portable (not requiring an electrical socket), so they could be placed wherever warm air was specifically needed. They were often used in unheated bathrooms, workshops, garages or greenhouses to provide a low-level background warmth. Paraffin was also a relatively cheap form of fuel at the time.
There were inherent dangers in using these heaters, however, the chief being that they burned with a naked flame and were a significant fire risk if knocked over or if the fuel was spilled. They also gave off nasty fumes as they burned, so if used within a confined space were particularly unhealthy. They were particularly popular with owners of allotments, as they allowed busy gardeners to stop and have a warming cup of tea in their shed whenever required!