#72 - Danish Industry or 'Dansk Industri' Stamps from 1968
. From what I have discovered, they were designed by R. Nellemann and engraved by Polish born, Czeslaw Slania - apparently the world's most famous engraver!"Engraving is an art process where lines, dots and dashes are cut into a soft metal plate with a tool called a burin. The engraving is done life size and in mirror reverse. Up to 10 lines per millimeter are cut at depths varying from 0.01 to 0.08 mm to give the effects of shadows, highlights and contours. Because engraving requires long years of study and an extended apprenticeship, it is used for high security documents such as postage stamps and banknotes."
You can actually see the dots and lines if you look closely at the stamps. I love the contrast between the graphics on the stamps (above) which are very simplistic and minimal next to the illustrations on the First Day Covers which are very sketchy and detailed...
The quote above is taken from Collecting the works of Czeslaw Slania
a site dedicated to Slania's work. Check it out for more information about his career or about engraving.