Vintage Summit collar by Austin Reed.
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 (the stud in the pictures is just for display).
Size: Collar size 15 3/4 (to fit shirt size 15 1/4).
Condition: Vintage collar, probably made around the 1950s/1960s. Never used, but slightly imperfect - there is a faint but visible mark (possibly pencil mark?) at the front, as shown.