Congratulations,you have inherited a nice silver salver that is over 200 years old. The salver was assayed in London 1780-81. The sponsors mark (Silversmith) is for Robert Jones I. This must have been one of his latter pieces since he had died by January 1783 when his wife registered her mark.
A little trick for London hallmarks is that if the Leopard has a crown, the date is before 1821. If there is not mark showing the current monarch’s head, the is dated before 1784. From 1784 to 1890 a monarch’s head is shown along with the other marks, this is a duty mark. The duty mark is also seen on all the assay offices.