Hieroglyphics
One of the great stories in cryptology over the last 200 years was working out the meaning of Egyptian hieroglyphics. This was the Egyptian writing of the old dynasties (the ones that had built the pyramids). The writing had fallen out of use and been replaced by different alphabets so that by the beginning of the common era (about two thousand years ago) there was no one left who knew how to read hieroglyphic writing. Throughout the next 1800 years, scholarly interpretations of this writing— and there are thousands of walls and obelisks with tens of thousands of lines of hieroglyphic surviving— ranged from the idea that the writing had no meaning at all as writing but was religious decoration to purely imaginary reconstructions of what the modern “scholars” wanted the hieroglyphics to say. The great breakthrough in understanding the real meaning of hieroglyphic writing came with the discovery of the Rosetta Stone in 1799. The stone carried a long government proclamation in three languages— the Egyptian script current at the time it was made, ancient Greek, and hieroglyphics. The intent was to have the information available to all, no matter what language they spoke. The benefit to modern scholars was they then had a coding sheet to break the difficult script of hieroglyphics.
Philately has had its own experiences with puzzles like hieroglyphics. Plating is the most obvious one. The first issues of most countries, including the United States, were printed by a method called line engraved. For the first few US issues the method was as follows: a die was prepared and the die was rocked into softened steel to create a transfer roll, usually of several impressions of the die. The transfer roll steel was hardened and used to rock the design into a larger plate, usually of 100, that was used to print the stamps. Because each stamp printing die of the 100 was rocked into the full printing plate with different pressure, very subtle differences exist on each stamp that are distinctive to the plate position from which it was printed. These differences are visible only under magnification and are often hard to see even if you know what you are looking for.