It is a type of slot machine in which the player must answer questions in addition to, or instead of, matching symbols.
Leading SWP manufacturers of the 1980s and 1990s were: Coinmaster, JPM, Barcrest, Bell-Fruit, Maygay and Ace-Coin.
Although many new quiz machines during this period actually offered lower jackpot prizes such as £5, and had gameplays and payout structures that seemed designed to frustrate professional players.
The arrival on the scene in 1985 of SWP/quiz machines quickly led to the existence of a cohort of professional and semi-professional players.
These were people who became highly skilled on particular games being able to learn and memorise nearly entire question sets for a particular machine.
Today it is still possible for very skilled players to make worthwhile money playing SWPs, but it is much harder than in the past.
An SWP machine must offer the chance to win the jackpot on every game; however, the level of skill involved to do that is set so high as to be virtually impossible.
Manufacturers have, at times, set the skill level so high that it is physically impossible to achieve this.