Re: Another Weird Wall Material
Before drywall became an acceptable wall covering, its first incarnation was known as "button board" and it was use in place of wood lath to hold plaster to the wall. The holes, or "buttons", allowed the plaster to squish through and key itself (lock onto ) onto the drywall. In the days of wood lath, it was the spaces between the lath where the plaster keyed onto the wall.
In answer to your question, you've got button board, brown coat plaster (first plaster layer ), and skim coat plaster (finished layer).
I suffer from CDO ... Its like OCD, but in alphabetical order, LIKE IT SHOULD BE!!!