#guan

Blue-throated Piping Guan (Pipile cumanensis), family Cracidae, order Galliformes, Poços de Caldas, Brazil

The wattle on the neck can be blue, black, purple, or gray.

Chinese Model GuanGuan (关关) for ADONISJING in Guan 2 Part 1

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Hi!

Do you mean this white band across the forehead?

In Chinese it's normally called a Mo'e (抹额) which is a name from the Tang Dynasty (there are several other names but this is the most common). It was usually worn by women and could be a slim strip of fabric or thicker, with lovely embroideries on top (using screencaps from Dream of the Red Chamber 1987):

There's some conflicting information on its origins, some people say it came about from the Shang Dynasty and was worn by both men and women at the time.

Another version says it came about starting in the Western Han Dynasty, with a strip of fabric wrapped around the head from back to front, and tied at the front. It could completely cover the hair on top of the head, or leave it exposed.

So I think whatever its origins, the first form of mo'e probably looked a lot different than in later dynasties.

Here's someone who replicated what was called "mo'e" in the Tang Dynasty:

(Original video here by 先生王騰, you can watch him demonstrate how to wear it.)

If you're talking about the accessory on top of the head, that's called a "guan/冠" (although the one in this photo I can't tell what it's made from...if it's made from fabric it's called something different, but I'm going to assume it's made from some sort of metal):

In historical China, at age 15 boys would put all their hair up in a hair bun as a sign of maturity (don't be fooled by the C-dramas, boys past age 15 wouldn't leave half their hair down in the past). At age 20, they have a ceremony where the man is given a man's hat or a "guan" as a sign that they are now an adult. Age 20 was also called ruoguan/弱冠 in China.

There are numerous types of guan, made from many different types of materials. A family's wealth, or status in society would govern what type of guan the men can wear (using screencaps from Romance of the Three Kingdoms 1994, many of the styles in the show have corresponding artefacts that have been discovered)：

19 Days