In the order in which you have posted pictures of the hallmarks:
London 1798, maker indistinct but probably Peter & Ann Bateman (PB over AB).
London 1815 by William Bateman I. The form of the duty mark shows that it was assayed between 1 Sep 1815 and 28 May 1816.
Exeter 1811 by John Legg.
In future posts please remember that not only will we expect only one item per topic but that it is also better if you do not use thumbnail images which require to be clicked on. Cropping pictures and adjusting sizes to suit forum requirements is not difficult and a little care (including getting in-focus pictures) will encourage us to make an effort on your behalf.