What a pretty plate! It is full of butterflies and other insects painted in overglaze enamels. There is lots of gilding. It measures 9-1/2".
According to 2 of my reference books, this style of plate dates mid-19th C to 1890. See Mudge's "Chinese Export Porcelain in North America" page 226, and the Schiffer's "Chinese Export Porcelain" page 29. The Schiffers say: "We have not found any of these marked " Made in China" or "China", though they could exist. We date most of these from the mid-19th century."
This plate is in excellent condition. There are no chips, no cracks, and no repairs. The foot rim is rough and shows some grit from the kiln. It rings when tapped. It is unmarked.