Social: There are a couple of important parts to this list of taxed items. At the end of the list are foodstuffs. A tax of food in one way or another is essential to provide for a hierarchy that does not till the land themselves. The provisions of fatlings and grain as well as the indication in verse 4 that these taxes are to support himself appear to indicate that King Noah (and most likely his priests and court) did not work the land themselves, but were fed from the labor of others.
The first part of the list is clearly metals. Sorenson provides the following information on Book of Mormon metals (edited to correspond to this list):
Copper, too, was well known anciently. The earliest metal artifact yet known in Mesoamerica is the bit of copper already mentioned. But copper was also basic to alloys. One alloy used in many parts of nuclear America was tumbaga, a mixture of gold and copper. Treated properly it had the “appearance of gold” but weighed less and probably was cheaper. R. H. Putnam has argued persuasively that the Book of Mormon plates that were in Joseph Smith’s hands were of tumbaga. (Had they been unalloyed gold, they would have been too heavy for a single person to carry.) A tumbaga specimen from Belize (British Honduras) shows that this material was known in the Maya lowlands no later than the fifth century AD
A different alloy is bronze, of copper with tin. The word bronze does not occur in the Book of Mormon, but “brass” does. The “brass plates of Laban” were brought from Jerusalem by Nephi, as we know. Until a few years ago it was supposed that what we call brass (an alloy including zinc) was developed only in the last few centuries. Yet the Bible speaks of “brass.” Bible scholars have dealt with that apparent misstatement by saying that the word translated “brass” was actually bronze. The Hebrew word now known to refer to both copper and bronze was translated in the King James Version of the Bible as several different English words (in Ezekiel 1:4, 27 it comes out as “amber”). Within the last few years, however, some ancient artifacts from the Mediterranean area have been tested by more sophisticated scientific techniques than before, and the tests reveal that actual brass, with zinc in it, was in use among the Etruscans, probably as early as Lehi’s time. That means that perhaps the brass plates of Lehi’s day are neither an anomaly of culture history nor an oddity of linguistic labeling, but of the literal metal.
…It is tempting to see “ziff” as tumbaga, for it is mentioned twice in direct connection with brass and copper (Mosiah 11:3, 8). Several derivations of “ziff” are possible in Hebrew with two general senses—“bright” or “shining” on the one hand and “plated” on the other. Both meanings would be appropriate for an alloy with a gilded surface. But “ziff” could also have been tin, another metal known in Mesoamerica. In fact, even mercury is a possibility, for it too occurred.
Iron use was documented in the statements of early Spaniards, who told of the Aztecs using iron-studded clubs. A number of artifacts have been preserved that are unquestionably of iron; their considerable sophistication, in some cases, at least suggests interest in this metal. (That is not surprising, since even a culture as simple as the Eskimo found iron—from meteors—valuable.) Few of these specimens have been chemically analyzed to determine whether the iron used was from meteors or from smelted ore. The possibility that smelted iron either has been or may yet be found is enhanced by a find at Teotihuacan. A pottery vessel dating to about AD 300, and apparently used for smelting, contained a “metallic-looking” mass. Analyzed chemically, it proved to contain copper and iron. Linne, the same Swedish archaeologist who made that find, accepted a piece of iron found in a tomb at Mitla, Oaxaca, as probably refined.
Without even considering smelted iron, we find that peoples in Mesoamerica exploited iron minerals from early times. Lumps of hematite, magnetite, and ilmenite were brought into Valley of Oaxaca sites from some of the thirty-six ore exposures located near or in the valley. These were carried to a workshop section within the site of San Jose Mogote as early as 1200 BC There they were crafted into mirrors by sticking the fragments onto prepared mirror backs and polishing the surface highly. These objects, clearly of high value, were traded at considerable distances. (This archaeologically established mineral processing was taking place within the valley that chapter I identified as the probable Jaredite land of Moron. The Jaredite record, a few centuries before the date of the San Jose Mogote finds, tells of the king who confined craftsmen who refused to pay taxes. There he compelled them to refine “his fine gold”—Ether 10:7.) But perhaps the strangest interest of all in iron materials on the part of the ancients has recently come to light (Sorenson, John L. An Ancient American Setting for the Book of Mormon. FARMS, 1985, pp. 282-5. See also Tvedtnes, John A. “Untranslated Words in the Book of Mormon” in The Most Correct Book. Cornerstone, 1999, pp. 344-6 for more detailed speculation on ziff).
Economics: We assume that gold and silver are precious, but this entire list of metals falls under the category of “precious.” The are specifically included as precious in verse 8. How is it that the other metals are also precious? The presence of brass as an alloy suggests that these things are not precious because of the ore, but because of the malleability of the metals. As was noted in Jacob, they are precious for what can be made with them, not simply because they exist (as with Asians, Mesoamericans would appear to place a higher intrinsic value on green jade than gold).
Just as in Jacob, the economics of the situation are important. Noah is in a land which was previously inhabited by Lamanites. Had ores been of the type of intrinsic value that gold was to the Spaniards, we might expect that the available gold would be already gone before the Lamanites were willing to give up the land. Nevertheless, in a single short generation (Zeniff already being of his majority when he joins the first expedition) Noah is able to tax specific workable metals.
The solution is precisely the same as we saw in Jacob. The value is in the goods created with the metals, not the existence of the metals. If there is sufficient of these metals to give a fifth part to the King, then while he would have more, he would not necessarily be significantly more wealthy that the rest of the population. It is the ability to exchange goods that yields wealth, and that exchange outside of the community that leads to wealth led to social and religious distinctions in the city of Nephi. Noah is back at the scene of the crime, in a very literal way, and he is repeating the same economic and religious errors as did the Nephites in Jacob’s time.