TASMANIA - OFFICIAL PERFINS
"T" used by State Government Departments (from 1902)
"OS" used by Commonwealth Government Departments (from 1904)
(5x5), (6x6), etc indicates number of holes in a T perfin (across x down)
5x5 was the most common format after c.1920.
N.B. this listing cannot be provided in a chronological order - sorry!