Metlox was a creator of homewares in Manhattan Beach, California. It was founded in 1928 and traded until 1989. This plate comes from the first line of pottery created called the 'Poppytrail' collection. This plate is in the 'apricot' colourway.
NOTE - I would recommend you keep this plate as a decorative piece as American pottery typically has lead in it's glaze and so isn't suitable for food use. This would look unreal as a wall plate.
