Some answers

4. What was Gutenberg doing in the second shop that earned him the gratitude of the future prince of Mainz?


1. It is possible that Gutenberg discovered that he could not apply enough heat and pressure to the base elements to reach the density of gold, but that he could mix an alloy of the same elements that looked like silver


2. Even though he could have made a silver-like alloy, would that be adequate? It seems more likely that he was hiding something "in plain sight." So the queston remains as to whether he was hiding something in the type or in the text.