Welcome to Tnet.
That’s a Fukagawa Seiji (Fukagawa Porcelain Company) mark… Mount Fuji with a stream in the foreground. They still make porcelain today from their factory in Arita in Japan. The remaining characters are blurred in your picture but it’s not their current mark so has a little bit of age to it. The “Made in Japan” sticker puts it after 1949 and more probably after 1952. I would guess it’s somewhere between then and the 1970s. Unfortunately not a valuable item.