New Finds
From the days when plastics were exciting:

“Leda-Beauclaire” dates only to 1958. After that, Beauclaire is dropped from the branding. On the 1966 Leda card at the right are real metal buttons.
The terms Permalite, Permaloid, and Permalon, may have referred to polyester, casein and nylon respectively on early Leda cards, or they may have just been marketing.
Embassy’s Satinsheen and Boilproof were used interchangeably in 1959, even for the same buttons, and were used for all plastic types.
By the 1970-80s, they just said ‘Buttons’, plain and simple! Plastic wasn’t glamourous anymore.