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I am no expert, but silk screen and copper plate transfer methods were probably used, and the method depends on the material the dial was made of. Pad printing, or a version thereof was likely used as well. You can Go to You Tube and see interesting demonstrations of these methods. The copper plate transfer method would likely utilize an engraved mirror image of a dial to which ink was applied, the surface cleaned, then the dial and copper plate put through a press of some sort, the ink in the engraving transferring to the dial. Go back far enough,many dials might have been hand painted.