See what I am talking about?
Perfectly black.
So first reason for this chocolate shade could be simple burning-out of case lid
Unfortunately we don`t have pictures of box interior ...
Let`s hope owner of this set will see this thread
For now let`s assume that it is not a simple consequences of "burning-out".
But what else it can be?
Any traces of brown cases?
Actually yes, but these cases have slightly different color and came from much earlier time period.
I am talking about quadro boxes from 1880s.
Let`s hit them!