Responsa for Bava Kamma 194:10

והא קא זיילין פירי אמר רב אשי חזינן אי מחמת טיבעא זיל מנכינן ליה

that there was an enactment that all kinds of money should be current in Jerusalem?<span class="x" onmousemove="('comment',' How then were Babylonian coins not current there? ');">¹⁶</span> — Said R. Zera: This is no difficulty, as the latter statement refers to the time when Israel had sway [in Eretz Yisrael] over the heathen whereas the former referred to a time when the heathen governed themselves.<span class="x" onmousemove="('comment',' A euphemism for Israel. ');">¹⁷</span> Our Rabbis taught: What was the coin of Jerusalem?<span class="x" onmousemove="('comment',' Cf. p. 556. n. 7. ');">¹⁸</span> [The names] David and Solomon [were inscribed] on one side and [the name of] Jerusalem on the other. What was the coin of Abraham our Patriarch? — An old man and an old woman<span class="x" onmousemove="('comment',' I.e., Abraham and Sarah. ');">¹⁹</span> on the one side, and a young man and a young woman<span class="x" onmousemove="('comment',' I.e., Isaac and Rebeccah. ');">²⁰</span> on the other. Raba asked R. Hisda: What would be the law where a man lent his fellow something on [condition of being repaid with] a certain coin,<span class="x" onmousemove="('comment',' V. p. 566, n. 4. ');">²¹</span> and that coin meanwhile was made heavier?<span class="x" onmousemove="('comment',' [The question is according to the view of Rab, ibid., that payment has to be made with the coin that had currency at the time.] ');">²²</span> — He replied: The payment will have to be with the coins that have currency at that time. Said the other: Even if the new coin be of the size of a sieve? — He replied: Yes, Said the other: Even if it be of the size of a 'tirtia'!<span class="x" onmousemove="('comment',' A quoit of certain size. ');">²³</span> — He again replied. Yes. But in such circumstances would not the products have become cheaper?<span class="x" onmousemove="('comment',' A larger supply being obtained by the heavier coin, and the increase would appear as usury. ');">²⁴</span> — R. Ashi therefore said: We have to look into the matter. If it was through the [increased weight of the] coin that prices [of products] dropped we would have to deduct [from the payment accordingly],

Teshuvot Maharam