Potteries changed ownership as well as names which can create confusion as to who made what.
The year 1730 refers to when the pottery was first built by Joseph Stubbs, not the year your item was produced.
The stamp "Keeling & Company Ltd. Late Mayers England" was used from 1909 - 1937. A stamp that shows the pattern name "Burton" over a kneeling man facing left, with 1790 in a box beneath and K & Co. under the date was made from 1886 - 1891.
The Pattern called "Burton" is very pretty. It features large, cobalt blue flowers and leaves edged in gold. Gold highlights also decorate the panel sided pitcher. There is a Burton teapot on Google images that is for sale on eBay. They are asking $130.00. Whether they get that or not is anyone's guess. Because pitchers and basins were often used and not stored in a china closet like a teapot, they were often damaged. I am guessing that the pitcher and basin would hold more value than the teapot. Just keep searching for more items in this beautiful pattern to get a better idea of the value. The values of Flow blue china can be different depending on the area where you live. In some areas, it is more popular than in other areas.