Old architectural salvage ironstone porcelain soap dish. This has a chrome plated mounting ferrule on the underside. It measures about 5 3/4" x 4". The socket is about 3/8" across.
We are also throwing in a cast iron mounting bracked that was being used with this. TWe don't think that this is the original bracket. The bracket measures about 3 1/4" long and 2" across the mounting face. The socket in the bracket is about 7/8" across and has a large hole broken in the bottom. The bracket also has chipping to the enamel and has been touched up with white paint.