Silver Black Stone Bangle Bracelet

This item is pre-owned for many years. I believe it was initially purchased from Belk Dept store I am not certain what the stone is but I believe it is a black onyx. See stamp on back of bangle in photo. Says 269 and Mexico. I don't know if this is sterling silver, as I do not see .925. I did find the same bracelet on another website which does label it as sterling silver and vintage. There are a few areas that are tarnished or darkened. See all photos.