Hi and thanks for your post. I am glad I can be of some help;
1) Your piece dates between 1740 and 1755 (the date letter is not clear enough in the photo). Try looking at the London date letters on this site! British Hallmarks
2) Assayed in London
3) Maker appears to be Fras. Spilsbury (Jacksons 3rd edition page 195)
Hi, The Maker is Francis Spilsbury (No1) This mark was entered on 15 June 1739 (See The Marks of the London Goldsmiths and Silversmiths 1697-1837. John P Fallon). Kind Regards Cas .