Hi, Leslie. I can not be sure what it is without seeing it, of course, but this sure sounds like Masonite. Masonite is made of wood chips in a resin glue. It did come prepainted in many colors. It comes in 1/8" and 1/4" thick 4'x8' panels, both solid and as pegboard. You might go to your local home center and look at some there for comparison. I have never heard any suggestion that it contained asbestos, but then I didn't expect to hear that kids wax crayons had it either.