The municipal authorities in cities in this state to which sections 87.380 to 87.490 are applicable, may, by law or ordinance, set apart one-half of all revenues received for municipal purposes by such cities from licenses issued by such cities for carrying on the business of a fire insurance company, agent or agency, and not exceeding three percent of all revenues received for municipal purposes by such cities from all other licenses issued by such cities, as a fund for the pensioning of members of the fire department, and of the widows and orphans of deceased members of the fire department of such cities, which moneys shall be credited to said pension fund.