This bangle has been shaved away to leave shiny diamond-shaped areas, alternating the textured sections. This style of bangle is found in different versions and various widths, with and without a resin wash, in Bakelite and also in transparent pastel shades of Lucite. See my shop logo for an example of a large red one with black resin wash. You can the shaved areas more clearly in that photo, but they are similar on this one.
This one is guaranteed to be Bakelite, and is almost 1 1/4 inch wide, and 1/4 inch thick at the points. The opening is almost 2 9/16 inches across.
Condition is very good. A slight roughness can be felt along the edges where the shaving was done but it not apparent to the eye.