1/20 marked on metal means, that 1/5th of the entire metal weight, (and in your cameo ring) will be 10 kt gold.
Goldstein & Swank Co manufactured silver-plated wares and jewelry - Worcester, MA, USA ca 1915 -1936
During the ages of world war in the 20th century, some metals were in short supply and these metals were directed, instead of towards making jewelry, towards making weapons & armory instead. Sterling silver was often substituted.
I'd be researching the year around the above dates, in the 20th century....
