This instruction booklet for Set 300 and Set 400 was introduced with the new Plastic Meccano range in 1971. In many ways it was clearly designed to give these more advanced sets the look and feel of "metal" Meccano sets and perhaps ease the transition for the younger age groups to move up into full Meccano. I think it was a great improvement over the large folded instruction leaflet that came with the older Sets A, B and C.