[a. F. billon ‘debased metal,’ originally certainly meaning ‘mass’ (Littré), i.e., ‘l’or et l’argent en bille,’ bullion, f. bille, BILLET of wood, etc.: cf. BILLOT. F. billon is cogn. w. Pr. billo, Sp. vellon, It. biglione, med.L. billi-ōnem. In Eng., of modern adoption from French, where its sense-development has not been clearly traced; it had at one time the sense now expressed by Eng. bullion, med.L. bulliōnem, and the two words have mutually influenced each other, though they are distinct in origin: see BULLION.]
1. A mixed metal used in coinage, consisting of gold or silver with a preponderating admixture of a baser metal. Also attrib.
1727. Chambers, Cycl., Billon, Billio, in coinage a kind of base metal either of gold or silver, in whose mixture copper predominates. Note. We don’t find ’tis naturaliz’d among us: but the necessity we are frequently under of using it in the course of this work, requir’d its being explain’d.
1797. Encycl. Brit., s.v. Billon, Gold under twelve carats fine, is called billon of gold.
1876. Mathews, Coinage, xxii. 231. For Martinique … small coins of silver and gold washed billon were struck in France during parts of the last century.
2. esp. An alloy of silver with copper, tin, or other base metal, in which the latter predominates.
1819. Rees, Cycl., s.v. Billon, The writers on numismatic science appropriate the term billon to signify metals of copper alloyed with a very small quantity of silver.
1852. Wright, Celt, Rom. & Saxon (1861), 378. Of these Richborough coins … fifteen [are] of billon or debased silver.
1883. C. F. Keary, in Antiquary, July, 260/2. The same king [James III.] issued several denominations of billon coins, as placks, half-placks, farthings.
