NOTE: This opalescent piece is in the pattern CORONA (OMN) originally introduced by Greenberg Glass Co. in 1893. Greensburg (2nd) was brought into the National Glass Co. in 1899 but was sold in 1900 to a bottle making glass company. Their moulds were moved to other factories with the McKee Works getting at least some of the Corona moulds. It is possible that this was made at one of the other National factories with the Indiana, PA works (formerly Northwood) or the Albany Works (formerly Model Flint) being the most likely candidates.