Duchy of Brunswick-Wolfenbüttel is the probably the wrong name

This 20 mark gold coin 1875 from comes from the "Duchy of Brunswick-Wolfenbüttel"
https://en.numista.com/catalogue/pieces67570.html

There was something called the "Principality of Brunswick-Wolfenbüttel" from 1269–1815 but it was not a duchy.
https://en.wikipedia.org/wiki/Principality_of_Brunswick-Wolfenb%C3%BCttel
More importantly from 1815-1918 it was the the Duchy of Brunswick
https://en.wikipedia.org/wiki/Duchy_of_Brunswick
I believe Duchy of Brunswick this in the correct label for this coin.

I don‘t understand, what is not correct?
We already have the Pricipality for coins before 1815 and the Duchy for coins minted after.

From 1815-1918 it was called the "Duchy of Brunswick" not the "Duchy of Brunswick-Wolfenbüttel".

Thank you, yes indeed.
Will ask for correction to the moderators.

The coin catalogue also uses Anhalt-Dessau for the The Dutch of Anhalt
https://en.wikipedia.org/wiki/Duchy_of_Anhalt

But ma-shops which seems to mostly a Germany company also uses Anhalt-Dessau
https://www.ma-shops.com/german-empire/

But they only use Brunswick not Brunswick-Wolfenbüttel. The Numista coin catalogue is consistent with ma-shops with the exception of Brunswick-Wolfenbüttel.

I don't know what Germany coins books use.