Most old maps in my home (ranging from a school atlas to professionally made large maps from the National Atlas of India) use a peculiar technology. Instead of colored 'dots', they use 'strokes' of continuous, straight lines oriented in different directions.
The following image is a portion of a map of South America from a school atlas published by a local publisher here in Kolkata (Chandi Charan Das and co., 150 Lenin sarani, kol-13. No mention of date or edition found, but it is a 15 to 20 year old book).
The word Caracas ( "কারাকাস" ) on paper is approximately 1.05 cm wide.
On a compound microscope (biology) (objective: 10X, eyepiece: 10X) but using reflected light, the lines do not show any 'dots' but instead uniform, continuous bands. The photograph below is taken from another map (on Asia, topography) from the same book.
The image on the left shows some vertical and horizontal lines. The one on the right shows some diagonal lines.
However the same school atlas also uses dot printing. There are also other maps which are solely made from dots, without any of these 'solid' lines.
An old map by the National Atlas of India, copyrighted in 1986, uses a similar pattern and probably the same technology. However, their grids are finer (narrower and more closely placed).
The width of the word "Chamoli" on paper is approximately 3.3 cm.
Could anyone help me identity this beautiful, old map printing technology?