These Leda buttons date from the early to mid 1960s. By this stage General Plastics, who originally produced Leda buttons, was struggling, and would be absorbed into Beutron (Aust). This resulted in the Leda buttons above being sold upon the Beutron type card with added cotton. The dark blue may still be made of casein, but the others are probably polyester.
Woolworths sold buttons for many years on a bewildering array of cards. The blue examples date 1957-1967, and the Sew ‘n’ Save 1967-72.