Same here, in Boston--It's covered in blue-green beetle wings, with absolutely exquisite embroidery on the cloak. Even in its current, faded state, you can see just how stunning this must have been when Ellen Terry actually wore it on stage.

Yes, the thought is that she was a young relative of/worker for the maskmaker; the mask was kept as an example of his work, became popular, and someone thought up the story of the lovely young suicide victim. She couldn't have imagined she'd be saving lives this long after her own ended...