You are bidding on a VERY NICE used example of a WW1 Imperial German Prussian Schirmmütze (Visor) or Tellermutze (Cap) Leather Sweatband! This was part of the standard cap used by the Army throughout the war. 

The Prussian army’s visor cap evolved from the enlisted mans "stable cap" in the early 1800's and was originally reserved for wear by Officers and Senior NCOs. In the early 1900's wear of the visor cap was extended to EM and Junior NCO ranks when off duty or in peace time. In 1907/1910 the German army introduced a new field-grey uniform, including headgear, to replace the previously worn dark blue uniforms. In 1915 after the outbreak of WWI the new 1907/1910 uniforms and headgear underwent minor modifications and were re-designated the M1915 uniform. On its introduction the NCO/Officer’s visor cap was issued with a branch of service, (waffenfarbe) colored centerband and piping.