1940’s (or older) vintage Czech glass sew-ons. They’re square shaped beads, and they measure about 5mm. They have flat backs with a single hole, and the color is a pale opaque grey. The top side is faceted into a pyramid-like shape. I also carry a very similar style — same size, shape and color, but with a textured or “bumpy” top.
Size = 5 mm
Quantitiy = 24 beads