ancient treasured sword
錕 refers specifically to an ancient treasured sword, a rare and valuable weapon from the past.
錕 combines 金 (metal) with 昆, which likely contributes the sound. The character was used historically for a specific type of ancient sword, but the exact origin of the compound is uncertain.
The left side 金 (metal) tells you it's made of metal, and the right side 昆 looks like a sword with a decorated hilt. Picture an ancient treasured sword forged from precious metal.
For コン, imagine a con artist trying to sell a fake ancient sword: con -> コン, and the metal sword is the treasure.