Not including the hanging chain, this shield measures 3 inches high, 2.5 inches wide. No hallmarks, made of coin silver. IOBA stands for Independent Order Brith Abraham. Because this is the shape of the Ten Commandments, I think this may have been used to decorate a Torah scroll used by that Boston chapter of the IOBA. The engraving has wear and is smooth to the touch, the whole piece is beautiful in person.

Examinations/pickups in person are welcome, I'm in New York City.