For the source text click/tap here: Bava Kamma 97
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Steinsaltz "The Gemara on our daf discusses the return of money in cases where the value of the currency – and, in particular, the coinage – changes while a loan is taking place.
To clarify the question about how to establish the value of coins that have gone out of circulation, Rava brings a baraita that discusses the case of pidyon ma’aser sheni. On certain years of the agricultural cycle, a farmer is obligated to bring ma’aser sheni – to tithe his crops and take them to Jerusalem where they must be eaten in holiness within the city. “
We explore the history of coinage from ancient times.