That story sounds like a total drag, but I getcha.
As for those two examples, I'm afraid that Antonio wouldn't really know either of those things- old weapons not so much, besides his own ceremonial King's rapier- and he doesn't have the knack for investigation / discovery of hidden passages.
No, I'm afraid Antonio's skills lie in other places- most likely his Charisma and his tendency to try for a leader position. As a King he understood and relied upon many, many royal advisers in mulitple fields- leading them and having them assist him where neccessary. Ergo, knowledge-wise though Antonio has a broad or shallow understanding in various topics, finding a clue that he alone could truly explain or recognise is likely to be difficult.
Still, not saying its impossible- and if you trust in your puzzle-making skills then I guess we'll see what happens, hm? Haha.