I just moved into a building in NYC that was built in the late 60s and I wanted to mount my 42" plasma. I drilled a few test holes after I used a stud finder and discovered the walls were about 2.5" thick. The drill bit went right through, I now have a peep hole to my bedroom. The other hole went in 1.25" and stopped. The dust looks like drywall/clay dust. The walls seem thick though, I can't hear people talking in the other room.
Any ideas what kind of walls I'm dealing with?
Should I abandon all hope of mounting my TV or anything for that matter? I was hoping to mount some shelves also.