Definition
A unit of Troy weight equal to twenty-four grains, or one-twentieth part of a Troy ounce. The term appears in historical legal and commercial contexts, particularly in trade and measurement law where precise weight standards governed the valuation and exchange of precious metals, coin, and apothecary goods.
Why It Matters in Research
This term surfaces almost exclusively in pre-modern legal and commercial documents — conveyances, trade regulations, assay records, and statutes governing weights and measures. Researchers encountering "pehn y weight" in historical sources should treat it as equivalent to the pennyweight (dwt), the standard unit of Troy weight still recognized today. The spelling variant signals an archaic or dialectal rendering; do not assume it refers to a distinct or divergent standard. Because Troy weight governed precious metals, coin, and pharmacy through much of Anglo-American legal history, confusion between Troy and avoirdupois systems was a persistent source of commercial and legal dispute. A researcher finding this term in a historical contract or regulatory document should confirm which weight system the broader instrument employs — Troy and avoirdupois ounces are not equivalent, and errors of system produce errors of calculation. Black's placement of this term in a supplemental section reflects its status as specialized vocabulary outside the core common-law lexicon, useful for resolving ambiguity in historical documents rather than for understanding a live legal doctrine.
Historical Dictionary Support
Black's Law Dictionary (2nd Ed.) Supplemental provides the only dictionary entry recovered for this term, defining it tersely as "a Troy weight, equal to twenty-four grains, or one-twentieth part of an ounce." The definition is accurate and consistent with the historical pennyweight standard. No substantive divergence exists among weight authorities on this measure: twenty-four grains to the pennyweight, twenty pennyweights to the Troy ounce, twelve Troy ounces to the Troy pound. What historical legal dictionaries do not address is the practical legal significance — namely, that statutory weights-and-measures regimes in both England and the American states often codified Troy weight for specific commodity classes, making precision in reading historical instruments essential. The term itself is absent from standard common-law dictionaries, confirming it is a technical trade and measurement term absorbed into legal reference works only incidentally.
Jurisdictional Note
Troy weight, including the pennyweight, was adopted as a legal standard in England and carried into American commercial and regulatory practice. Modern U.S. and U.K. statutory weights-and-measures frameworks have largely displaced older terminology, but the Troy system remains in use for precious metals and gemstones. Researchers working with historical American or English documents should consult the applicable jurisdiction's weights-and-measures statutes for the period in question.