The example on the left has faux stitching around the edge. this dates it from 1951-2, as in the below advertising.
The “Opal-Glo 660” card is a mistake! The buttons are not style 660. They are rather examples from around 1958 of Tecpearl buttons.
This style of ‘colour matched’ card was not used for long, only from around 1966-68. They were replaced by the style on the right until the mid 1970s.
This card, from the mid 1970s, shows a convincing ‘pretender’. Although entirely plastic, it looks like it has a woven centre!
See the G.Herring/Beutron page for more details on dating Beutron buttons.