This is later revealed as a lie; Slugworth is actually Mr Wilkinson, one of Wonka's workers.
The proposal is a test Wonka set up to judge the worthiness of the ticket holders to take over the factory, given to all five children.
An actual Everlasting Gobstopper prop used in the 1971 film was sold for $US100,000 to the owners of the television show Pawn Stars.
[1] A product called the Forever lasting Gobstopper was introduced in 1976 by the Chicago candy company Breaker Confections.
[2] The Willy Wonka Candy Company brand was later bought by Nestlé, and production has been moved to Itasca, Illinois, US.