Wooden Buttons, made from Cedar ply.
 
These buttons are handcrafted using cedar charred by the Japanese yakisugi (or shō sugi ban) method. The surface of the wood is charred, without burning it, creating a chemical process of cell changes that produce a more water resistant surface through carbonisation.
We can't say for certain if these buttons are waterproof,  but the treatment offers a stunning look to the already striking cedar ply.
Slightly darker than image shows.
 
Circa 1960s/70s.
30mm diamter.
[Larger sizes may be available in store]