Vintage detachable collar, Radiac style number 2.  Early 20th century.  

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.

Size: Collar size 16.5 (to fit shirt size 16). 

Condition: Vintage collar, around a century old.  Still nice and white, but with noticeable scuffs, wear and fading, as shown.