Pinchbeck is a form of brass

Brass

Brass is an alloy of copper and zinc; the proportions of zinc and copper can be varied to create a range of brasses with varying properties.In comparison, bronze is principally an alloy of copper and tin...

, an alloy

Alloy

An alloy is a mixture or metallic solid solution composed of two or more elements. Complete solid solution alloys give single solid phase microstructure, while partial solutions give two or more phases that may or may not be homogeneous in distribution, depending on thermal history...

 of copper

Copper

Copper is a chemical element with the symbol Cu and atomic number 29. It is a ductile metal with very high thermal and electrical conductivity. Pure copper is soft and malleable; an exposed surface has a reddish-orange tarnish...

 and zinc

Zinc

Zinc , or spelter , is a metallic chemical element; it has the symbol Zn and atomic number 30. It is the first element in group 12 of the periodic table. Zinc is, in some respects, chemically similar to magnesium, because its ion is of similar size and its only common oxidation state is +2...

, mixed in proportions so that it closely resembles gold

Gold

Gold is a chemical element with the symbol Au and an atomic number of 79. Gold is a dense, soft, shiny, malleable and ductile metal. Pure gold has a bright yellow color and luster traditionally considered attractive, which it maintains without oxidizing in air or water. Chemically, gold is a...

 in appearance the idea being that ordinary people could buy gold 'effect' gems when gold was only sold in 18 carats which pushed the price way over what people could afford to pay. Invented in the 18th century by Christopher Pinchbeck

Christopher Pinchbeck

Christopher Pinchbeck was a London clockmaker and maker of musical Automata. He was born in Clerkenwell but worked in Fleet Street. Probably his name was derived from Pinchbeck, Lincolnshire. In the 18th century he invented the alloy Pinchbeck a cheap substitute for gold...

, a London

London

London is the capital city of :England and the :United Kingdom, the largest metropolitan area in the United Kingdom, and the largest urban zone in the European Union by most measures. Located on the River Thames, London has been a major settlement for two millennia, its history going back to its...

 clockmaker. The inventor allegedly made pinchbeck jewellery clearly labelled as such. Pinchbeck jewellery was used in places like stagecoach

Stagecoach

A stagecoach is a type of covered wagon for passengers and goods, strongly sprung and drawn by four horses, usually four-in-hand. Widely used before the introduction of railway transport, it made regular trips between stages or stations, which were places of rest provided for stagecoach travelers...

es where there was a risk of theft

Highwayman

A highwayman was a thief and brigand who preyed on travellers. This type of outlaw, usually, travelled and robbed by horse, as compared to a footpad who traveled and robbed on foot. Mounted robbers were widely considered to be socially superior to footpads...

. Later dishonest jewellers passed pinchbeck off as gold and it came to mean a cheap and tawdry imitation of gold.

Pinchbeck typically comprises copper and zinc in ratios between 89% Cu, 11% Zn; and 93% Cu, 7% Zn.