Maaser Sheni, Chapter Four, Mishnah Two
This mishnah deals with various laws concerning the evaluation of maaser sheni when it comes time to redeem it.
1) Maaser sheni may be redeemed at the lower market price:
a) At the price at which the shopkeeper buys and not at which he sells.
b) At the price at which the money-changer takes small change and not at the price at which he gives small change.
2) Maaser sheni may not be redeemed in an estimated lump.
3) If its value is known, it may be redeemed according to the evaluation of one.
4) But if its value is not known, it must be redeemed according to the evaluation of three, as for instance in the case of wine which has formed a film, or produce which has begun to rot, or coins which have become rusty.
Section one: The mishnah provides two examples that illustrate the rule that maaser sheni can be redeemed at the lower market price. The first is what we call wholesale, and not retail. The second has to do with the exchange rate. When a moneychanger takes small coins and gives the customer a large coin which would be easier to carry to Jerusalem, he takes some percentage for himself. When he gives small change, he gives less small coins for the large coin. Today this is similar to the different rates you get at the bank whether you are buying dollars (your foreign money will be worth less) or selling dollars (the foreign money you buy will be more expensive). When one comes to exchange small maaser sheni coins for a large one, he can estimate the value of the larger coin at the higher rate, so that it counts for more small coins. This will save him some money.
Section two: When one redeems maaser sheni, he must measure the produce, either by counting how much there is (ten jars of wine) or how much it weighs (two seahs of wheat).
He cannot make a lump of the produce and estimate how much is there.
Section three: If the value of the produce is known, then only one person is needed to estimate its value. We should note that normal produce would have a typical market value.
Section four: The evaluation of produce or coins that are beginning to deteriorate requires three people, because its value cannot be determined solely on their market value. Since it is more difficult to evaluate and people might disagree, it requires more people to do the estimate.