Antique upright "cricket" collar.  Appears to be made of celluloid, probably late Victorian.  Depth one-and-a-half inches.  

Size:  Marked as size 47 cm/18.5 inches, but it actually measures as size 18 inches.  Probably best worn with a 17.5 shirt.

Condition: Vintage collar, clean and unused, but with some minor scuffs from storage, as shown.