Australia Official OS Stamps

Australian Official Service or OS stamps, introduced in 1902, were punctured or overprinted OS for use in Federal Government departments. Their use was to signify the mail was for official purposes and presumably to try to stop fraudulent use of the stamps by employees.

The first punctured or 'perfin' stamps were were punctured with a large size OS but the holes weakened the stamp so that the perfins were reduced in size to a smaller OS from about 1913 onward. A medium size OS was used in 1927-29 on three commemorative issues. There is also what is referred to as the NSW perfin as the "S" of "OS" had 12 holes, as compared to 11 found in most small OS; this only used for New South Wales state departments.

	Perfin	Dates/Issues	Size
	Large OS	1902 to 1914	14mm high, 15mm wide with 19 holes in "O" and 17 holes in "S"
	Medium OS	1927 Canberra, 1929 Western Australia Centenary &1929 Airmail	10mm high, 14mm wide with 12 holes both in "O" and "S"
	Small OS	1913 to 1930	7.5mm high, 15.5mm wide with 12 holes in "O" and 11 holes in "S"

The perfin was replaced by an overprinted OS in 1931 and the use of the OS was withdrawn in 1933. Maybe the employees were stealing them for their collections!