What is a second label button hole attached with buttons for?

[dorward]

I've seen a waistcoat and jacket which each have a pair of buttons behind the lapel which are used to attach a small piece of fabric containing a button hole just above the normal button hole.
Can anyone tell me what the purpose of this is please?
Thanks.

 

[Papperskatt]

To close the collar. Very good for cold/windy weather.

 

[dorward]

To close the collar. Very good for cold/windy weather.

Ah! There's no matching button on the other side though, so presumably this is a decorative one.