Thanks, but I have lived in 70's houses as a kid. I won't do that again. It's 2006, MDF.That looks to me like someone put a 1/8 chip board over the top of the sub floor, maybe even over another layer of vinyl. Which was pretty common in my area in the late 70's and 80's. If it was me I would replace the floor down to the studs. IF your house is 70's or 80's then suit and mask up, seal off, and filter and exhaust the air as you work... If you can't guess why I am saying that then you should not proceed.