Identify a wallcovering-plaster type coated wallpaper

[dexterxx]

I am trying to strip wallpaper from a HSL which initially looks like a normal heavily embossed paper that has had several layers of paint.

However it will not budge and the parts I have got off seem to resemble a backing paper covered in a thin layer of plaster type coating. Quite shiny, like a hard chalk consistency. It cannot be impregnated with water it needs to be chipped off.

I doubt this would have come on a roll. The design is too consistent and covers a large an area.
It is not a plaster texture finish also the material is not a crumbly as plaster. It could be a paper Mache type of thing. Has anyone come across this and if so is it possible to remove or is it better to plaster over the top?