Dickey Collar

Like the detachable shirt collar, the dickey (a bosom-front for a dress shirt) was invented as a separate accessory for the shirt, which thus could be washed, starched, and pressed more readily than could be laundered if the dickey were an integral part of the shirt. https://en.wikipedia.org/wiki/Dickey_(garment)

How do you use the collar?

The Dickey collar is actually just a half-shirt that you put on over part of your chest, then just slip on a sweatshirt, tank top, or blouse, and it’ll give you that put-together look without having to wear so many layers. https://www.womanandhome.com/fashion/fashion-news/this-viral-fake-collar-fashion-trend-is-taking-over-spring-fashionand-its-only-dollar9/
Shoulder: 35 cm
Length: 28 cm