This article claims a breakthrough in decoding Indus script. It builds on the author’s earlier papers which established Indus script’s use in taxation, and trade/craft licensing, and discussed how different segments of the semasiographic Indus inscriptions encoded different information (tax-types, license-categories, commodity-names, tax-paying modes, tax-rates, tax-receiving entities, etc.). This paper claims that certain inscribed needle-shaped gold artefacts found in a jewelry hoard of Mohenjo-daro, and a similar gold-tipped copper stylus found from Kotada-Bhadli, were gold-assaying needles used with touchstones. Such touchstones, sometimes gold-streaked, are found from Mohenjo-daro, Banawali, etc. Revealingly, the way modern gold-testing needles bear the words “gold” and “karat”, Mohenjo-Daro’s gold-testing needles bore signs and . This study claims that the frequent Indus sign symbolized a blowpipe inside a crucible , and metonymically signified gold, precious metals ( ) and gold-smithy (sign clearly depicted the fire below crucible). Crucible-blowpipe-based words and symbols have signified metal-smithy in ancient Egypt, Mesopotamia, and India. It also identifies sign , which symbolized Abrus precatorious seeds, and signified the related ‘ratti’ (raktikā) based weight-system. ‘Ratti’, India’s traditional gold-measuring and numismatic unit, was the basis of Indus civilization’s weight systems. In certain inscriptions ( ), , a modified “ratti”-symbol, occurs as a metrological term related to gold . In Indus inscriptions, fish-like signs (e.g., , , ) occur frequently with precious-metal symbols ( ). Interestingly seals/tablets containing fish-like signs, are mostly found near Indus lapidaries, bead-factories, and jewellers’ shops. This paper argues that fish-like signs signified gemstones, lapidary activities, related precious commodities, and corresponding weight standards. Since ancestral Dravidian languages were spoken across Indus settlements, Indus scribes possibly applied the ancient Dravidian homonymy, where the polysemic Proto-Dravidian fish-word “mīn”, a popular fish-word of India, also signified ‘shining’, ‘bright’, and ‘gemstone’. Relevantly, the eye-patterned apotropaic gemstone-beads imported from Indus valley were called fish-eye-stones (“NA4-IGI- ḪA”, “NA4-IGI-KU6”) in Mesopotamia.