Wavy-edge plates are quite common, wavy-edge dishes turn up now and again, but this is the only wavy-edge charger we have seen -- and it's a desirable 20-inches to boot!. Surely you must have an empty 20-inches somewhere! Maker's touch (barely legible) on underside for James Spackman, London, (1704-1758). Heraldic armed fist holding a pen on rim.
Details and more photos.