The I-SPY books are spotters' guides written for British children, and particularly successful in the 1950s and 1960s in their original form and again when relaunched by Michelin in 2009 after a seven-year gap in publishing.
The I-SPY Tribe was based on the I-SPY Books, some forty small volumes that sold in hundreds of thousands. Each book covered a subject such as I-SPY Cars, I-SPY on the Pavement, I-SPY Churches, I-SPY on a Train Journey, etc. As children spotted objects such as coalhole covers, oak trees, semaphore signals, fire engines, whelks, and so on, they recorded the event in the relevant book, and gained points. Once the book was complete, it could be sent to Big Chief I-SPY for a feather and order of merit.