St James Medallion old rare hard to find

St James Medallion found in water by a Mariner; received as gift approx 50 years ago. I have not found another quite like it rare, The package it came with says Anno Domini 1083 which is Medieval Latin and means "in the year of the lord" non magnetic weight is 11 grams If someone can identify the four figures on the back this medallion send me a message or write if other concerns.