Glossary

Money that is legally valid for the payment of debts and must be accepted for that purpose when offered. Each jurisdiction determines what is legal tender, but essentially it is anything that when offered (‘tendered’) in payment of a debt extinguishes the debt. There is no obligation on the creditor to accept the tendered payment, but the act of tendering the payment in legal tender discharges the debt.

The lettering, words or phrases that are engraved on coins, usually located along or around the outside edge of the coins.

Central banks usually fulfil the function of ‘lender of last resort’. To ensure financial stability, the central bank provides emergency credit to financial institutions that are struggling financially and near collapse, for example if they no longer have other available means of borrowing, and where their failure to obtain credit would dramatically affect the economy. An example of when this is needed is if bank account holders withdraw funds at a level and in a timespan which means the bank cannot liquidate assets fast enough to match the demand, creating what is known as a ‘run on the bank’.

An array of lenses, designed so that when viewed from slightly different angles reveal different parts of an image. The most common example are the lenses used in lenticular printing to give an illusion of depth, or to make images that appear to change or move according to the viewing angle.

A multistep process consisting of creating a lenticular image from at least two existing images, and combining it with a lenticular lens. This process can be used to create various frames of animation (for a motion effect), offsetting the various layers at different increments (for a 3D effect), or simply to show a set of alternate images which may appear to transform into each other.

A relief printing process by which many copies are produced by repeated direct impression of an inked, raised surface against sheets or a continuous roll of paper. Letterpress printing remained the primary means of printing and distributing information until the 20th century, when offset printing was developed, which largely supplanted the role of letterpress in printing books and newspapers.

A commonly used means of grading security features created by the European Central Bank and adopted for use across the banknote industry. Level 1 refers to features that can be verified by the public, untrained examiners or specialist examiners with the naked eye. Level 2 refers to semicovert features that require some form of reading device or tool to be authenticated. They are typically deployed for use by retailers, cashiers and inspectors but are also detected by sensors in machines (the ECB defines Level 2a, 2b and 2c). Level 3 refers to covert features, generally rare chemicals or compounds that can only be identified by sensors in high speed processing machine verification used in cash centres. Level 4 authentication uses forensic examination to verify banknotes and is used solely by central banks/police.

Manipulating the width, length and height of line structures to create image and text effects. Using a higher resolution for the output results in effects not possible with commercially available software.

Chemicals that have properties between those of conventional liquids and solid crystals. Orientation of the crystal-like structure of the chemicals results in optically variable effects. Cholesteric liquid crystals have two refractive indices, a property known as birefringence (the ability to rotate the polarisation of incoming light and reflect circularly polarised light either clockwise or anticlockwise). Liquid crystal technology is used for security features that are validated with a polarisng filter.

A collective term for the effects of colour change or other visible characteristics under different sources of illumination.

An umbrella term for solving problems for which development of algorithms by human programmers would be cost-prohibitive, and instead the problems are solved by helping machines ‘discover’ their ‘own’ algorithms, without needing to be explicitly told what to do by any human-developed algorithms. While artificial intelligence encompasses the idea of a machine that can mimic human intelligence, machine learning does not. Machine learning aims to teach a machine how to perform a specific task and provide accurate results by identifying patterns.

A security feature requiring an instrument to verify its presence or data content.

The ability of a computer to see. The technology and methods used to provide imaging-based automatic inspection and analysis for such applications as automatic inspection, process control, and robot guidance, usually in industry.

An ink containing ferromagnetic components that have a specific reaction to the external magnetic field. Text or symbols applied by this ink can be identified by special magnetic sensors or visualised by magneto-optic converters. The ink can be applied on security threads and fibres,and used for printing images, serial numbers and barcodes.

An analytical technique to quantify known materials and identify unknown compounds within a sample and elucidate the structure and chemical properties of different molecules.

Traditionally, a coin-shaped artistic piece with no face value, made for religious, honorary and other commemorative purposes.

One million pixels. The term is used not only for the number of pixels in an image but also to express the number of image sensor elements of digital cameras or the number of display elements of digital displays.

Printing ink containing metallic components that provide a metallic finish to the applied substrate.

The coating of films or surfaces with a very thin layer of metal using a metal deposition technique. Metallisation is what gives holograms their silver or similar metallic appearance.

A pair of similarly shaded inks, the colour and contrast of which appear virtually identical in normal light, but which have different spectral responses so that, when viewed in another light (such as infrared), one ink displays different effects or colours to the other. In the case of IR pairs, one ink absorbs IR and the other reflects it, and only the IR-reflecting part can be seen through a filter.

Thin 2D metamaterial layers that allow or inhibit the propagation of electromagnetic waves in desired directions.

Small lenses, typically only a few microns in size.

Tiny microscopic mirrors created using origination techniques similar to those used for diffractive OVDs (optically variable devices). Micromirrors reflect light in a specific manner defined by the size and orientation of the mirrors.

A unit of measurement commonly used in authentication when referring to the thickness or gauge of physical substrates and features. One micron is equal to one millionth (10-6) of a metre.

Optical systems that are between a few micrometres (millionths of a metre) and one millimetre in size, including small lenses or arrays of lenses.

Lines, symbols, designs, images or numbers that are printed at dimensions barely perceptible to the unaided human eye but visible at magnifications of between x5 and x10 by (say) a jeweller’s loupe. Microprinting on banknotes usually combines positive and negative characters.

The very small scale structure of a prepared surface of a material as revealed by a microscope above 25× magnification. Diffractive microstructures comprise microprotrusions or microgrooves, or a combination thereof, which are capable of diffracting lightwaves.

An industrial facility manufacturing coins.

A letter or symbol, indicating a mint of origin.

A fibrous composition of the substrate used for banknotes, containing fibres of cotton and other materials such as linen or polyester. The purpose of using mixed fibres is to improve the mechanical properties of the paper, such as scratch or crinkle resistance.

A mobile payments system based on accounts held by a mobile operator and accessible from subscribers’ mobile phones.

An app for storing financial information and other documents such as credit cards, bank information, and even driving licences.

Large-scale interference patterns produced when a partially opaque ruled pattern with transparent gaps is overlaid on another similar pattern. For the moiré interference pattern to appear, the two patterns must not be completely identical, but rather displaced, rotated, or have slightly different pitch.

Broad categories that measure the money supply in an economy. In the US, labels are attributed to standardised monetary aggregates: M0 – physical paper and coin currency in circulation plus bank reserves held by the central bank; M1 – all of M0 plus traveller’s cheques and demand deposits; M2 – all of M1 plus money market shares and savings deposits.

Monetary law is the legislative and regulatory framework that provides the legal foundations for the use of monetary value in society, the economy and the legal system.

From the Latin word ‘moneta’, money is any item that is generally accepted as payment for goods and services and repayment of debts, such as taxes, in a particular region, country or socio-economic context. Its onset dates back to the origins of humanity and its physical representation took on very varied forms until the appearance of metal coins. The banknote, a typical representation of money, appeared in the 17th century, and has since experienced great development and growth. Currently, electronic systems allow payments without the need to deliver physical money (banknotes or coins). Money is considered to have three basic functions: unit of account, medium of exchange and store of value.

The illegal process of making large amounts of money generated by a criminal activity, such as drug trafficking or terrorist funding, appear to have come from a legitimate source. The money from the criminal activity is considered dirty, and the process ‘launders’ it to make it look clean

A coin, token or medal whose obverse design is not matched with its reverse.

A diffractive image in which different, usually unrelated images appear at different viewing angles. The most usual, and easiest to make, are images that flip from one to another as a DOVID is tilted from side to side. The most difficult is an image that changes as the DOVID is rotated.

Captures image data within specific wavelength ranges across the electromagnetic spectrum. The wavelengths may be separated by filters or detected with the use of instruments that are sensitive to particular wavelengths, including light from frequencies beyond the visible light range (ie. infrared and ultraviolet). Multispectral imaging can allow extraction of additional information the human eye fails to capture with its visible receptors for red, green and blue. 

A unit of measurement commonly used in authentication when referring to the thickness or gauge of physical substrates and features. One nanometre is equal to one billionth (10-9) of a metre.

The science and technology of precisely manipulating the structure of matter at the atomic and molecular level. In the authentication sector, nanotechnology is used to explore and develop unique optical phenomena for use in new material and security features.

In general, refers to the central banks of different countries that are part of a currency union.

The part of the electromagnetic spectrum between 780nm and 2500nm, near-infrared is the region closest in wavelength to the red light detectable by the human eye.

When the nominal interest rate drops below 0% for a specific economic zone. This effectively means that banks and other financial firms have to pay to keep their excess reserves stored at the central bank, rather than receiving positive interest income. This is hard to enforce while people have the option to hold funds in other assets, particularly physical cash.

The value or units of banknotes (or coins) issued by a central bank over a period, minus the equivalent withdrawn from circulation during the same period. A positive net issuance expresses an increase in circulation during the period.

The value stated on a coin or banknote, ie. face value.

The study of paper money or banknotes.

System used in some countries in which the central bank delegates the safekeeping and distribution of banknotes to private entities and offers some sort of financial compensation to incentivise the system. See also Balance sheet relief mechanism.

Numbering enables a banknote to be differentiated from another banknote of the same denomination. If two banknotes have the same numbering it is proof that one of them is false. Numbering is usually on one side of the note, but can be on the front or the back.