Diane E. Wirth discusses the monetary system in Alma 11; argues the text is not discussing coins but instead is a system of weights and measurements.
Diane E. Wirth, A Challenge to the Critics: Scholarly Evidences of the Book of Mormon (Bountiful, UT: Horizon Publishers & Distributors, Inc., 1986), 46-48
Most ancient coins of the Old World origin found in the Americas are determined to have been brought here after the Conquest. The Book of Mormon has been criticized on this basis; however, where in the Book of Mormon text is the word “coin” used>
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Critic and even some LDS writers, often assume that the monetary names used in the Book of Mormon refer to coins. However, nowhere in this record is the word “coin” mentioned.”
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Conclusions
The word “coin” does not appear in the Book of Mormon text.
The Nephite monetary system is concerned with measurements.
Several Nephite words for various weights and measurements have their origin in Egyptian and Hebrew words.
Bartering of weighed and/or measured goods, be it of grain or metal, was considered a method of exchange in Mesoamerica.