Vintage Button 1950s? Sparkly Gold Cut Steel? Black Concave Glass 19mm

Size: 19mm
Material: this is black glass, but I am unsure what the edges are. The face is concave - very hard to tell when it's a reflective jet black surface! I am querying cut steel on the edges?
Condition: good vintage condition - some backs are flea bites and age lines
Number of buttons: Price is per button and I have four buttons in stock

We use Australian coins for size reference - 5c, 10c, 20c and 50c. We also provide a millimeter ruler for accurate sizing. 

We are not button collectors, nor do we know a lot about them. Our drive is to keep as many of these beauties out of landfill. All of our buttons are sourced secondhand. Some are used, some are unused - some are very old (antique or vintage) and some are modern and new. There may be wear, tear and occasional discolouration, but if it's listed we consider the buttons still good enough to use and save from landfill. We'll list as much information as possible and provide close-up photos, but if you have further questions please don't hesitate to use the Contact Form or email vintagefabrics@gmail.com.