The black stone (probably hematite) intaglio seal is intricately engraved with several lines of angular cursive script into nashk which dates the seal to between the 10th and 13th centuries (Porter, 2011). The engraving possibly translates to a name or phrase bearing religious significance. 

The circular cut stone with a rare dotted border is set within an intricate later silver mount (probably dating from the late 19th to early 20th century) with engravings running across the band. 

For referenced seals in the British Museum see items 192, 337 and 340 in ‘Arabic and Persian Seals and Amulets in the British Museum’ (Porter, 2011). 

UK size R, US size 8.5

The ring weighs 5.14 grams, the stone measures 10mm x 9mm, the ring is unmarked but tests as high-grade silver. 

For British Museum seals: https://www.islamicmanuscripts.info/reference/books/Porter-2011-Arabic-Persian-seals-amulets-BM.pdf