Mystery and magic

My mother, now aged 85, has a small gold cross pendant with a diamond chip. She has had it for at least 65 years, and it held inside it a surprise that mystifies me still. The back of the cross had a tiny pinhole. When you held the hole to one eye, you could read the entire Lord’s Prayer. In a day when nothing was digital or computerized, it is a wonder that print could be made so small. How did they do that!?