Vintage silver plate mustard pot with blue cobalt liner very nice condition unmarked original liner unfortunately I can't find any information on Hallmarks makers name etc but it is a heavy well made item 7 cm tall 5 cm round some age related wear 
The earliest form of mustard pot, dating from the late 17th century, was the blind caster and the current form of mustard pot did not become common until the late 18th century. The pots usually have a glass liner to facilitate cleaning and often have a small matching silver spoon (with an oval shaped bowl).