The collar is made of cotton organdy with cross stitching. The collar is bound with cotton bias binding and hand-stitched into the neckline. This is something you very commonly find in dresses that have small side or shoulder openings. It allows the wearer to easily clean the part of the garment that got dirtiest. Removable collars are more common in men's clothing.
Opening: 2 1/2" placket on the right shoulder that closes with 3 Size 0 snaps.