This is a Ko-Imari, sometsuke (blue and white) mukouzuke (small serving dish), also usable as a soba choko (soba noodle cup). Perhaps it's called a tsutsu-mukouzuke (cylindrical serving dish)? It can be used as a mukouzuke or a soba choko, making it a wonderful and versatile piece. I've kept these carefully stored in a wooden box for many years, but I've decided to sell them separately, dividing them into perfect condition and those that are not. Both of these are in perfect condition, and I think they have a very rare and lovely atmosphere. Although they are in perfect condition, one has a kiln mark on the bottom, as shown in the photo, so I've discounted it slightly for those who may be concerned. Approximately 9.3cm in diameter x 6.5cm in height.