It measures approx.  7 ¼” x 4 ½” x 1 5/8” deep

Sometsuke, hand painted in under glaze blue, with ryusui-ayu, a trout w/ stream pattern, a shape of
chrysanthemum also known as kikka-gata, a lobed rim with iron glaze

Similar design is found in the book, Shibata Collection IV, No.283
Archive
Mid Edo
1720 - 1770
Hizen Imari Porcelain
No.115
Sometsuke Ayu-mon Kikkagata Plate  
 
1760 - 1790