What style of collar is this?

[Sackcloth]

The man depicted is supposed to be Vincent van Gogh, and since I trust the BBC with regards to historical accuracy, I assume it was a contemporary style in the 1890s, but I've never seen it named. I'd appreciate any assistance from one of this board's many knowledgeable members.

[storeynicholas]

It's a neckband shirt and has a stud at the front and one at the back to take a separate collar (often, but not necessarily, stiff). Some firms call these shirts 'tunic shirts' but a tunic shirt is really one that has a tunic front, that is a solid panel below the first four or five buttons. You need a collar 1/2" larger than your normal collar size to go over the neckband.
NJS

[Sackcloth]

Ahh, that would explain why I've seen the style on only a few period photographs. And of course, a bohemian like van Gogh would not always care to wear it with the collar attached. Thank you.