Beautiful plate! The background has a millefiori (aka mille-fleur) pattern with three windows.
The overall impression it gives is that it could be Japanese. If it is Chinese it will have be from the 20th century, the mark did not exist before. What makes me also think it could be Japanese is the shape of the three windows, which is a classic shape frequently found in Japan (not only on porcelain).
I cannot help with this, I'm afraid as I am limited to Chinese porcelain, but I recommend you try asianart com. Their forum has some regular visitors who are knowledgeable in Japanese art. You could also try to find more information by searchng for "millefiori" or "mille fleur" patterns.
