The name Ace of Diamonds isn't based on the sword's history or legends. It's purely about the shape of the weapon.
Compare the swords carefully.
A's grip is the same red color as the diamond on an ace of diamonds card. B has a diamond-shaped decoration on the cross-guard at the base of the blade, and a diamond pattern on the handle. C has an actual diamond in the handle.
But are any of these features enough to call the sword Ace of Diamonds?
All the swords are hung up on display and out of use now, but at the time the Ace of Diamonds earned its moniker, it would have been used as a weapon.
Perhaps its opponents called it so based on the shape it had from their point of view? In other words, from the end of the blade?
Look carefully at the shape of each of the blades as seen from the end of the blade, including the cross-guard. One of them must have a shape befitting the name Ace of Diamonds.
The ace of diamonds is a playing card. What shape are playing cards?
Solution
Incorrect
Too bad.
That one doesn't have the necessary quality that would lend it the name Ace of Diamonds...
Correct
Correct!
Sword A is the Ace of Diamonds. Anyone who's ever seen it from the pointy end knows why!
