Kriegsmarine carbon monoxide tester or CO-Anzeiger made by Auer

Rare original complete Kriegsmarine carbon monoxide testing device or CO-Anzeiger manufactured by Auer. The device seems to be complete and is in overall very good condition. The lid shows a nice tag which names the devices and also shows the serial number: Fabr. Nr. 6472. These devices were used by U-boat personnel and were indispensable because it protected the crew for carbon monoxide poisoning! This is the first time that I have encountered this device, nice and rare Kriegsmarine piece of equipment!