There are no labels on this collar.
It looks as if it might have been intended for use with a cardigan, or possibly a sailor suit.
It does not look as if it has been used.
There are no button or stud holes.
Perhaps it was intended to be pinned on - or perhaps it needs to have press studs or buttons and button holes added?
Measurement straight across the back of the collar (from point to point) is 17 inches.
Measurement from centre back to centre of front parts is 13 inches.