فَإِذَا بِيعَتْ بِجِنْسِهَا مُتَفَاضِلًا جَازَ
Translation: Exchanging such coins for their kind with a difference in quantity is permissible.
This concerns coins predominantly composed of base metal, not silver-predominant dirhams. Fath al-Qadir notes that where silver still exists on both sides as a component, relevant sarf possession rules and allocation constraints continue to matter.
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Unequal exchange of predominantly adulterated coins
Bab al-Sarf: Mixed Currency Exchanges, Debased Coins and Obsolescence
فَإِذَا بِيعَتْ بِجِنْسِهَا مُتَفَاضِلًا جَازَ
Translation: Exchanging such coins for their kind with a difference in quantity is permissible.
This concerns coins predominantly composed of base metal, not silver-predominant dirhams. Fath al-Qadir notes that where silver still exists on both sides as a component, relevant sarf possession rules and allocation constraints continue to matter.