These cheap plastic 3D viewers became popular in the late
1950’s. This one, which was purchased in September 1960, was linked to Weetabix
cereal, and could be purchased by sending one shilling and sixpence and a voucher
attached to a cereal packet. Every packet of cereal contained one of the
twenty-five cards in each series, which included “Animal Cards”, “Our Pets”, “Working
Dogs” and “British Cars”.
For further information on the 3D viewers, consult Wikipedia: