....AN EXERCISE INMICRO CONCEALMENT....
The document above is a March 2nd, 1891 special edition of the Daily Telegraph newspaper ex Sydney. That makes it 132 years old.
It looks quite normal at this size but the original, which I have, is just 6.3 inches wide by 9 inches in height.
To put it another way and to convert it all to millimeters, it is 158 mm wide and 230 mm in height. That makes the font size approximately .4 mm in height in its original form. Could it have been reduced even further? I think so.
This particular edition folds out to 4 pages including numerous illustrations.
The question for everyone is simply this, do you think that the Military would have seen other uses for this technology at the time?
The method included the use of a technique known as 'zincography'. Essentially printed text and images were photographed and then etched onto a zinc plate using an acid. In this way they were able to reduce the size of an image, the forerunner of microdot technology.
If you so wished, you could conceal other text or handwritten information within the images or the larger text heading of the page, could you have concealed the whole page behind another?
Here's an example of what was achievable by the advent of WW2. In this case, I've used some fairly modern technology to demonstrate the point:
Could it have been done? It was possible and there was an image 10 years ago that showed something very similar with a page from a Rubaiya carrying many lines of micro text but not visible to the naked eye.
And here's a link to an ABE Books item,
a Miniature edition of the Rubaiyat from 1903