1. “Engraved double image”
a “latent image” type coin security feature of the Royal Spanish Mint
commemorating the 500 th anniversary of Christopher Columbus (1451 – 1506)
Columbus taking possession of the new country (1492)

2. The man who changed the course of history
An original manuscript of Christopher Columbus
The man who changed the course of history
Presentation of the coin by the Royal Spanish Mint (front)

3. The Royal Spanish Mint commemorates the 5th century of Christopher Columbus with the minting of a silver coin with a fineness of 925 thousandth and a face value of 12 euros. A great treasure which comprises 500 years of history, an homage to the first man who dared to look far beyond the horizon. A coin of historical value, a tribute to the most influential person of our history.
Presentation of the coin by the Royal Spanish Mint (back)

4. “Engraved double image”
A coin security feature of the Royal Spanish Mint
The present invention relates to a process for obtaining double picture prints on any kind of hard surface, which process is particularly useful as a security system and a constituent element in designing coins, medals and the like, so that the said process allows two different pictures to be viewed on the same relief, being alternately visible depending upon the impingement of the light, i.e. one of the pictures will be visible in a given position and on tilting the piece slightly the said picture will be concealed and the other will come to light.
In the preferred field of practical application of the invention the double picture print system prevents the coins from being copied using matrix systems traditionally used in counterfeiting.
From: Diaz Salas, Zamorano de Blas, Latorre Barrena, Jose, Fabrica Nacional de Moneda y Timbre,
“Process for obtaining double picture prints on hard surfaces”, EP A1, published 3 May 1995.

5. Cristóbal Colón - Christopher Columbus
(1451 – 1506)
illumination in diffuse reflection at 45° from top.
Coin diameter 33 mm.

6. Diffuse illumination from the right

7. Diffuse illumination from the left

8. Microphotograph with stereo-zoom microscope and diffuse illumination from the right.
Line thickness converted to image contrast

9. Microphotograph with stereo-zoom microscope and diffuse illumination from the left.
Line thickness converted to image contrast

10. Microphotograph with stereo-zoom microscope and diffuse red illumination from the left and diffuse green illumination from the right, in order to distinguish between left and right furrow walls.
Observe this illustration from a few meters distance to see both images combined (image detail 7.5 x 10 mm).

11. Red illumination
Green illumination
Green image removed
Red image removed

12. Toggle between this slide and the next slide
Microphotograph with diffuse illumination from the right.
(6 furrows/mm)
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13. Toggle between this slide and the previous slide
Microphotograph with diffuse illumination from the left.
(Same area as previous slide)
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14. Cross section of engraved furrows
(schematic)
furrow top
furrow
furrow bottom
Basic unmodulated furrow pattern
Furrow pattern with angular image modulation
bas-relief in left furrow wall (image I)
bas-relief in right furrow wall (image II)
adjacent bas-relief of both images

15. 3D-overview of image modulated furrows
bas relief in left furrow wall
left furrow wall
right furrow wall
bas relief in right furrow wall
furrow top
furrow
furrow bottom
From: Diaz Salas, Zamorano de Blas, Latorre Barrena, Jose, Fabrica Nacional de Moneda y Timbre, “Process for obtaining double picture prints on hard surfaces”, EP A1, published 3 May1995.

16. End of presentation