The value of the Treasure Mirror, evidently, was beyond that of a 'treasured item' worth a thousand taels of silver.
In theory, for such a big transaction, the shopkeeper wouldn't be able to decide on his own—no matter the type of pawn, he would need to consult with the backers of the shop.
However, the shopkeeper of Li Zhen Pawnshop had significant autonomy because he had powerful backers, and he caught the hint given by Steward Li. Thus, he offered An Jing a convenience, "However, three hundred taels of silver is indeed too heavy to carry in cash. I wonder if you accept our Da Chen's silver notes . . ."
"Is gold not acceptable?"
An Jing frowned slightly, feigning dissatisfaction, while the shopkeeper shook his head with a bitter smile, "Ah, Xuan, you haven't been in Da Chen for long and perhaps are unaware of our situation . . . here, gold is exceedingly precious!"
The people of Dust Li generally do not accept silver notes; they only want cash or gold.