You had me intrigued, so I surfed a bit.
Found many references to Kaufman-Essex.
All showed the fibre content as
55% linen, 45% cotton.
There is a metallic line that is 50% Linen/40% Cotton/10% Lurex Y/D Cloth.
Didn't find anything referencing Cotton & Flax as the designer.
However, linen is made from flax, so I am wondering if that is where the mix up is?
Some of the links I found .... starting with Robert Kaufman themselves ....
https://www.robertkaufman.com/fabrics/essex/#more_info
https://www.fabric.com/buy/fh-751/ka...-blend-natural
https://www.hancocks-paducah.com/SHO...ssex-Yarn-Dyed
https://www.missouriquiltco.com/shop...oyster-yardage
The metallic line is really calling to me ... just gotta see it IRL!!!