Definition
An obsolete term from medieval monetary practice referring to a square piece of gold coin, commonly valued at thirty pence. The term appears in early English legal sources and glossaries as a unit of currency with a fixed conventional value, used in the context of monetary transactions, fines, payments, and valuations appearing in older legal instruments and records.
Why It Matters in Research
Researchers encountering *cusa* in historical legal documents — particularly in medieval English records, manorial accounts, or ecclesiastical instruments — should treat it as a monetary denomination rather than a physical description of property or goods. The valuation of thirty pence is the figure carried forward through the glossary tradition from Cowell's *Interpreter*, and that figure should be treated as a conventional approximation rather than a market rate, since the actual purchasing power attached to the term varied by period and context.
The primary research trap is confusing *cusa* with other archaic coin designations that appear nearby in glossary sources. Historical legal dictionaries list the term tersely and without elaboration beyond Cowell's authority, meaning researchers cannot rely on those sources to resolve ambiguities about valuation in a specific document. Where the precise monetary value of a payment or fine is legally material in a historical dispute or probate or title matter, the Cowell citation in Rapalje & Lawrence exhausts the mainstream glossary support; additional authority would need to come from numismatic histories or specialized medieval monetary scholarship outside the standard legal dictionary shelf.
The term has no modern legal currency (literally or figuratively) and will not appear in contemporary statutes, regulations, or case law. Its relevance is confined entirely to the interpretation of historical instruments.
Historical Dictionary Support
Rapalje & Lawrence transmit the definition directly from Cowell's *Interpreter*, identifying *cusa* as "a square piece of gold coin, commonly valued at thirty pence." This is the terminal point of the glossary tradition on this term — no elaboration, no dispute, no alternative valuation is offered across the standard historical dictionary shelf. The entry in Rapalje & Lawrence is notable for what immediately follows it: the definition of *manceps*, sourced separately to Wharton, suggesting the editors were compiling rare and archaic monetary and contractual terms in sequence without cross-linking them. Researchers should not infer any legal relationship between *cusa* and *manceps* from their proximity in the text.
The reliance on Cowell throughout the historical dictionary tradition means that any limitation in Cowell's original research propagates forward uncorrected. Cowell's *Interpreter* (various editions from 1607 onward) was a glossary of law terms rather than a numismatic authority, and his monetary valuations for archaic coin terms were not always rigorously sourced. The thirty-pence figure should be used with that caveat in mind.
Jurisdictional Note
The term is rooted in English legal usage and appears in sources within the English common law glossary tradition. No equivalent usage has been identified in Scots, Irish, or colonial American legal sources.