Background/Story
Electroplated glass button.
This one came in a small box of deadstock Japanese school uniform buttons. Some of them show wear that reveals the body of black glass.
I decided to investigate by breaking a few using a hammer and a chisel. Among those that are indeed black, one had the core of green glass. It resembles the one found by a beachcomber near Kamakura, Japan. Read the story on WRBA.
For more info, refer to p. 38 of the Clear and Colored Glass Buttons by Jocelyn Howells and Debi Michel Chrowl, p. 36 of the Black Glass Buttons handbook by Joan Lindsay and Simone Kincaid, “Silver Embellishment on Buttons” by Herman Bangeman (NBB October 2003 ), and the October 2019 article “Q&A silver deposits on buttons” by Joy Journeay (NBB October 2019).