Here is a special Écorce made for Boucheron, which look to be completely different from the the Parker production Écorce.
The material is also different as this Boucheron pen is made of sterling silver as seen by the "925" hallmark indicating it is made from 92.5% silver. The Parker production Écorce is gold- or silverplated brass.
This pen was depicted on page 145 in the French book "Un Amour de Stylo" by Robert Laffont, The description accompanying a photo of this pen was:
Parure Parker. Boucheron, argent et or motif écorce
which translates to:
Ornamental Parker. Boucheron silver and gold bark motif
My guess is that the book's use of the word écorce was only descriptive, and not to state authoritatively that this was the model name.
I previously listed this pen as an unknown pattern (#10) when I was shown a French 1991 auction catalog.
The item description was "Exceptionnelle parure de stylos en or blanc massif décor écorce." which loosely translates to "Exceptional ornamental pen designed in solid white gold with bark decoration". Based on the above close-up picture we know this pen is not made of white gold, which in France would have been required by law to be solid 18K.