What is a "Fire mark"?
Over a hundred years ago, this was a round (or other shape) iron, copper or lead emblem that was usually placed, on the wall, near the front door of a structure. It denoted the insurance company who had a policy on that property. It was usually made of enough metal to be able to withstand a fire.
The earliest fire marks may have been created soon after the Great Fire of London in 1666. After this fire, London created an insurance system and "fire companies". Once you paid your insurance and affixed the fire mark to your structure, you would have the services of one of the city charted companies. Fire marks (insurance company marks) were used in the U.S. from about 1750 to around 1900.
In the early days of the U. S., there were no municipal fire departments. Fire brigades were sometimes either owned, or paid, by insurance companies (or assurance companies) or supported by the community. Some stories tell that in some communities the fire brigade only responded to protect the property of those who had the insurance who owned this fire brigade. In other cities the fire brigades might have been independent companies. The story you hear, tells of the money going to the fire brigade who was successful in staking a claim on the property, which was on fire. One method of claiming a structure was to place a ladder on it. The first company to do so was allowed to fight the fire and was therefore paid by the insurance company. As you can imagine, there were problems with this system. Fire companies would have people whose main job it was to (A) ladder the building and (B) prevent the other company from doing so. There are many, apocryphal, stories of different fire brigades being involved in fist fights, in the front yard, while the structure burned.
But the thought that a burning home, with no fire mark, was left to burn, was probably not true. In fact, in the U.S., there is no evidence to support this belief. Volunteer fire departments were supported by community donations and many other sources of revenue. The insurance company's fire mark was possibly more of an indication of a "reward" for saving a particular structure, if anything other than advertising. For this reason one might hear of fire companies fighting over who would be allowed to fight a fire. Not all insurance companies paid a reward, but some may have. Much like today, some insurance companies simply donated money to the local volunteer fire departments. Only about one in ten insurance companies ever issued fire marks, so their value, or purpose, remains unclear. It is possible that a fire mark would have a different purpose or meaning depending upon the insurance company, the community, or the insured.