Undercollar for German field jackets. Cotton, white side to neck, dark side to collar of a jacket. We used dark green fabric for this batch, this colour suits perfectly for 1936 jackets with dark-green collars.
The undercollar should be buttoned inside the collar (different manufacturers of field jackets sew these buttons on various distance, and 2 side buttons probably shall be moved).
Undercollar was obligatory before the war, these had been used also during the war untill shirts with collar were introduced. The undercollar protected neck from rubbing and a collar of field jacket from greasing and wear-out.