Slug (coin)

A slug is a counterfeit coin that is illegally used to make purchases. The object substituted may be an inexpensive object such as a washer or a coin from another country with far lower purchasing power than the coin it is being passed off as.
While slugs are sometimes passed off to cashiers and other unwitting human recipients, they are more commonly used in automated coin-operated devices such as a vending machine, payphone, parking meter, transit farebox, copy machine, coin laundry, gaming machine, or arcade game. By resembling various features of a genuine coin, including the weight, size, and shape, and/or by mixing it with genuine coinage a slug is intended to trick the recipient into accepting it as a real coin.
Losses caused to vendors by slug usage may be the result of the loss of sales revenue following the distribution of merchandise that was obtained at the vendor's expense as well as the loss of cash that is distributed by the machine for overpayment with slugs. Honest customers may also suffer losses when change returned for overpayment is in the form of a slug rather than a genuine coin. Customer losses may be either unintentional on the part of merchants (such as when perpetrated by unwitting cashiers or machines designed to automatically process previous payments as change for later customers) or the result of the deliberate substitution of genuine coinage by corrupt cashiers and vending machine operators.
Though slug usage is illegal in the United States and elsewhere, prosecution for slug usage is rare due to the low value of each theft, the difficulty in identifying an offender, and also the difficulty in proving mens rea (especially when the slug is another country's genuine coin) since perpetrators when confronted will often claim the substitution was an "honest" mistake. Offenders in casinos are most likely to be prosecuted, as casinos have high levels of video surveillance and other security measures, and tend to be more proactive in enforcement.
There are many cases of genuine coins being used as slugs in another country, with or without knowledge of the user.
Slugs are usually made from metals differing from those of real coins. While genuine US coinage is made from various alloys of copper, nickel and zinc, Canadian coins are made mostly from steel with some copper and nickel, and euro coins are made from steel, nickel, and brass, slugs are frequently made from differing metals and alloys that are cheaper to obtain and mold, such as aluminum, tin, and lead.
Slugs may or may not have the face details of real coins. Some slugs that are made to match the face details may not be immediately recognizable as such to handlers, and may enter circulation.
Older, cheaper, and other low-tech machines that have fewer security measures are more likely to be defrauded by slug users. As an example, the fully mechanical mechanisms used in the traditional type of small vending machines that distribute candy or toys, and that can still often be found today at the entrances and/or exits of grocery stores and other retailers, can be fooled by cardboard coins. Many newer machines, especially those found in casinos, have additional detection that can identify more details of coins and detect those that do not resemble real coins.