The wall was made of a material called rock-lath. A description of that material is found here http://www.usinspect.com/resources-for-you/house-facts/basic-components-and-systems-home/interior-home/wall-and-ceiling-cove-2
This was quite a bit harder and messier than drywall due to the plaster coating on the material.
There are always surprises when you open up a wall and we were lucky this time. Only one surprise! The wire mesh around windows and corners was not foreseen.
This was taken care of with a tool called a dremel – this great You Tube video describes how to use it.
As I mentioned in my previous post, care was taken around the cove ceiling. A chisel was used to remove the wall below the cove.
Below is the chisel and dremel used for this project.
Finally – the completely open wall with a cut out of cardboard to show how our TV and future possible speaker would look on the wall. Mission accomplished for the day.