A vintage spare shirt collar - choice of colours.
These collars were originally supplied as "extra" collars for "Pintail" shirts by Seercraft.
They are not "separate" collars, but were intended to be sewn onto the shirt as replacements, once the original collars were worn out.
Difficult to date.
I believe that Seercraft traded until the late 1970s, but judging by the style of the collars and material, I would guess that these were probably made in the 1960s.
There is no size marked on the collars, but they measure 16 1/2 inches along the neck hem.