I am at the very beginning stages of mounting my 32" flat panel on the wall. I was not able to find any wall studs with various different stud finders, so I assumed the my walls were plaster. This also seemed to make sense since this house is 1940's construction. I figured I would remove the plaster until I reached the lathes to make it easier to install the outlet, all the behind the wall wiring and find the wall studs. Low and behold, I discovered that the top layer of the wall is actually 1/2" sheetrock with another type of wall underneath the sheet rock. Any help with identifying the type of wall would be greatly appreciated. It is very brittle, and is 1" thick. Here are some pics.