Bosch 6V horn set HO/FSA 6/15 6/16 390 530hz

Rare 6V Bosch HO FSA 6/15 and 6/16 horns with 390 / 530 hz in used condition. The horns are a matching pair, possible in original first color paint and without dents. The power and ground plastic connectors are without damages but one “screw head” is missing. I put with my old charger 6 Volt on it and both did makes noise, but not very loud. Also, my charger gave up after few seconds. They need strong power from a battery and may start running. 15 cm diameter, 3000g heavy and made in Germany. The horns were mounted on a fire truck.