Those who locate the prized coin and tweet a photo of it to @HeienekenUK with the hashtag #ItsYourCall by 11.59pm tonight (18 August) will be in with a chance to win a Rugby World Cup prize package.
One lucky individual will be invited to Somerset House on 26 August for the official Heineken launch of Rugby World Cup 2015, where they will meet Carling and claim their prize.
The prize package includes two VIP tickets to the opening match between England and Fiji on 18 September, as well as an opportunity to stand with the team captains at the official coin toss.
The VIP match experience will also include Heineken hospitality and a tour of Twickenham stadium, meanwhile the winner will receive the 1991 match coin as a memento.
Heineken unveiled details of its Rugby World Cup activations in July, which included a mention of social activity and use of the #ItsYourCall hashtag.