and in today's world, a charger is what they call the large plate that sits underneath your dinnerplate. Popular for holiday entertaining, often in gold, silver, green, red, metallic colors. Can be found inexpensively in import shops Just cosmetic I think, today. But they might have been used as a sort of place-mat to keep food from slopping onto the tablecloth. All the courses are served on the charger, except dessert. The servants remove the empty plate and place the next course on the charger. Or so I heard - don't have servants - and if the charger rim gets slopped on? No idea.
Your portrait plate may also be called a "cabinet plate". Meant for display. And yes, they are called chargers also. Just not meant to sit under your dinner plate. If you need help identifying the maker, post back. And check out e-bay sales too. KB