Vintage Stamped 925 Silver Banded Black Onyx & Marcasite Pierced Earrings

These earrings measure 5/8 of an inch long by 1/4 of an inch wide. The backs lock nicely into place. They feature bands of onyx and Marcasite set in sterling silver. Stamped 925. One of the tiny Marcasite pieces seems to have been lost and replaced by a small disc, see photos. It could have been made like this as it matches very well.