Vintage detachable shirt collar.   Marcella collar for evening wear.  Probably made around the 1930s.  Textured cotton.
Size:  17.5  inches (to fit shirt size 17).
You will need a pair of collar studs to fix this collar to your tunic shirt.   These studs are NOT included, but are available separately. 

Condition...Vintage collar, many decades old, and  in very good, clean, condition. Freshly laundered, but not starched.