Vintage Mexican Sterling Silver Amber Heart Ring Size 4.5

This ring is a sweetheart ring given to me by my first boyfriend! It is an amber heart split into two sides of a dark and light amber with sterling silver running down the center. This may be green amber as it is similar to a ring on the Larimar site. Amber is also a common material used in rings made with Mexican silver. The hallmarks on the inside indicate 925 Mexico along with some symbols I am researching. Materials - 925 Mexican sterling silver Stones - unknown - looks like Amber. Measurements - measure across is 15.1 mm which corresponds to US size 4.5 on Pandora Canada ring chart. Go by measure.