(1.) This is perf 12. Perf 10 also exists.
(2.) In the perforating process a small piece of paper, in this case it is round, is actually removed. (3.) Exp:do. Ref: Scott catalog.
(1.) Serrate roulette 13.
(2.) The rouletting process differs from the perforating process in that during rouletting no paper is removed. The paper is weakened by cutting it in certain locations. What is taken from one stamp when they are torn apart, becomes part of its neighbor. Rouletted stamps can be recognized by the little tuft of paper remaining when they are torn apart.