The Reverse Water marks of the Small Papua Lithiograph Issue. (SG49 to SG71) – By Mark (Robbo) Robinson (ASP V10N4)
The term reverse watermark implies that the watermark appears as a Mirror Image of its normal state. Such watermarks can only be detected if the watermark itself is not symmetrical. The letter A used in the watermark for the Papua Lithographs is asymmetrical having a second leg parallel to the right-hand leg of the A, thus making reverse watermarks detectable. Illustrations of the normal and reversed watermarks when viewed from the gummed side of the stamp (as per Stanley Gibbons) are shown.
For the full article, refer to V10N4.