Here's a thought, after looking at it some more. Is it possible this could be a
fibula? I haven't seen any examples of an Egyptianizing
style fibula, but the
style of manufacture, with the convex
reverse, resembles that seen on
some zoomorphic fibulae. Looking at my object, I see depressions on either end which could be remnants of a pin mechanism and L-shaped catchplate. On the other hand, I have not seen any examples in this
style, although that may not mean much. The catchplate and hinge mechanisms on these tend to break off and leave slight protrusions, rather than depression, although it's not unheard of, especially if they were made of a different material.