Australia - Brown years: 1923-1939.
Ordinary rate delivery envelopes: AB-EO-

General characteristics:

Heading and notes: No form number.
TELEGRAM in red at top above window.
Message area: Blank.
Reverse side: Blank.
Colours (text & envelope): Red on cream to grey.
Size of envelope overall: 81 × 136 mm.
Distinctive characteristics of this form:
 In 1920, the Universal Postal Union met in Madrid at their 7th Congress and accepted the recommendation for member countries to use window deliveries for postal and telegraphic use. The transparent section had to be an integral part of the envelope and it had to allow:
  1. the address to be easily read through the window;
  2. a specified area for the date stamp

Australia accepted the UPU recommendations on 1 January 1922 and authorised the use of window envelopes as from 1924. Formats for delivery forms had to be altered to enable window envelopes to be used with the address positioned in an appropriate location (see AB-DO-3 and AB-DU-3).


Used ordinary rate window delivery envelope.


  • "CHARGES ..." left justified and TELEGRAM (not underlined) to the right;
  • the window is placed very high.
AB-EO-2A (reverse).

Reverse side of the above delivery envelope showing the shape of the flap and the colour of the security pattern showing through.

AB-EO-2A open AB-EO-2A (reverse).

Reverse side of AB-EO-2A opened to show the fine security pattern.


Used at Dubbo 22 April 1935.


  • TELEGRAM is slightly right of center;
  • "CHARGES ..." are left justified and a space below TELEGRAM;
  • the window is much closer to the base.
AB-EO-2B open

AB-EO-2B (flap open).


  • flap has a rounded peak and deeply curved sides;
  • same security pattern as for AB-EO-2A although lighter;
  • has Printer's insignia INVICTA REGISTERED.

Used ordinary rate window delivery envelope.


  • TELEGRAM (underlined) and "CHARGES ..." left justified;
  • the window is much closer to the base than for EO-2A.

The evolution of subsequent issues of window envelopes and their many variations can be evaluated in terms of present UPU and ISO standards:

Rectangular items shall be considered standardized if their length is not less than their width multiplied by √2 (approximate value 1.4). These items shall satisfy the following conditions:

The transparent panel for the address of the addressee shall in addition be at least:

The panel may not be bordered by a coloured band or frame. Service indications may be placed just above the addressee's address.


Details of use and rarity.

Schedule number Earliest recorded date Rarity rating
EO-2A None.   NC
EO-2B None. 22 April 1935 at Dubbo, NSW. NC
EO-2C None.   NC