Detachable white cotton soft collar.  Rocola Supersoft, style no 277.  Probably made shortly after (or possibly just before?) the Second World War.
You will need a pair of collar studs to fix the collar to your tunic shirt.  These studs are NOT included, but are available separately.

Size: Collar size 15.5 (to fit shirt size 15).

Condition: Vintage collar in good condition (used) but not perfect.  Has been recently laundered.  Slight yellowing along the fold line.