That is just amazing. The skills that existed in the past have been totally lost over time. It's like the safelight I bought recently that was made in the late 1800's, and is powered by a candle! Who knew?
In comparison to the relatively huge Stanhope images, microdot film images the size of a typewriter's period were used many decades ago to sneak secret information past censors. They could replace a dot in the typescript.