An unlikely instrument for a band that never played one on record — until you trace the connection to John Lennon’s mother, Julia, who taught him “That’ll Be the Day” on her own banjo. That thread of authenticity is likely what pushed manufacturers to add a Beatles banjo to the wave of mid-’60s musical-instrument tie-ins.

Mastro introduced five plastic guitar/ukulele models at New York's 1964 Toy Show, from the 30½" "Beatle-ist" down to the 5½" "Pin-Up" brooch. Made from Dow Chemical's resonating polystyrene "Styron," each carried band faces and facsimile autographs, shrink-wrapped with a pick and songbook. Selcol produced seven similar U.K. versions. As one Mastro craftsman put it: "We made so many ukuleles... we sold so many instruments."