1883 ISSUE

"OS" in Black on 1877 Queen Victoria 2p Blue on White laid paper.

Envelope size: 138 mm x 78 mm.
 

"G.P.O." in three concentric ovals. With "Specimen" overprint.
With round "O" and slanted "S" in "OS".

"G.P.O." and "N.S.W." in three concentric ovals. 

Mint envelope with oval "O" and slanted "S" in "OS".
Used by the Government Printing Office

1895, APRIL 25: SYDNEY to KEMPSEY
2p Envelope with black obliterating bars for ordinary use 
by the general public still used officially.

VERY SCARCE