Hi,
You have to check the standard mark or the Lion Passant in combination with the London city Assay Office mark and relevant date letter.
Different date letter cycles of first 20 letters have been used, date letter cycles with upper or lower case letters, Gothic letter cycles, and in combination with different shape of the date letter shield. Different shapes of the London Leopard’s head with crown and later without crown, and different appearance of the lion standard mark and shape of the shield; Lion Passant (looking straight forward) & Lion Passant Guardant(looking left) .
http://www.925-1000.com/silverglossary4.html
Duty mark - Kings Head later Queens Head: in 1784 a duty was imposed on all silver, and was ordained that the representation of the head of the sovereign should be stamped on all plate to show that it had paid the duty. This was continued until 1890.
Looking at the date letter chart below; perfect match, the missing dot in the maker's mark probably due to a worn punch and perhaps the roundness of the surface of the napkin ring.
NB:
BEWLAY & Co Ltd were registered importers, retailers and pipe mounters who were identified in Assay Office's ledgers as "tobacconists", "pipe makers" or "pipe mounters".
http://www.silvercollection.it/DICTIONA ... NISTB.html
Oel.