Antique Cup and Saucer - H&B - rd 135869

I picked up these cups and saucers at the Car Boot sale yesterday for £2. They are marked H&B under a crown, and it stands for Hibbert & Boughey, a Staffordshire pottery. One of the cups and saucers has a rd number 135869, which dates it to 1889. Apparently this pottery only existed for one year with this name, so that is the date for these cups and saucers. They are not in great condition and before I washed them they were covered in little brown dots, which sort of wash off. I wonder if it's some sort of Iron stone and its rust coming through. I will put this in the category China and dinnerware, and tea cups and saucers, and as usual I will probably get an email saying it's been recatagorised to the above!!