Final answer:
Coelho mentions the beautiful sword in the market to highlight its significance and rarity.
Step-by-step explanation:
Coelho mentions the beautiful sword in the market to highlight its significance and rarity. The sword is described as being made of multiply-refined iron and has never been seen before. It is specifically made for a marquis or a king, emphasizing its value and exclusivity. Coelho uses the mention of the beautiful sword to create a sense of wonder and allure in the setting of the market.