For an excellent article on the history of Formstone, (and permastone, etc.) please click here.
Another method of applying the stones was buying tm pre-made and sticking them up.
Manufacturers sold the pre-made stones and shipped them to the jobsite. This explains permastone applications where
the stones are identical, with maybe 3 or 4 stones repeating themselves.
Another method was hand tooling the stones. The stone joints were hand tooled in the brown coat, and colored
by a color finish. This method was evident on close examination or the stones.
Like many other building trends, permastone has become obsolete. Remember T-111 plywood from the 70's ?
Unlike T-11, permastone is an incredibly durable finish, as evidenced by how much still is in place.