Hi
Great item.
Date - Agree with 1767. Very distinctive (unique?) "M" date letter.
Maker - The mark is very rubbed. However, it looks like that the mark is italicised, begins with maybe a "W" and in a quite unique looking cartouche. Options:
1. On this page here (
http://www.silvermakersmarks.co.uk/Make ... WA-WB.html) - which I think is run by Forum regular PhilO? - there is an unidentified mark for WA which bears some resemblances to your mark. Date fits.
2. Another possibility is William Grundy (
http://www.silvermakersmarks.co.uk/Make ... WF-WH.html). Date fits.
If I had to go with one, I'd go with Grundy. Known for making tea pots, and the mark seems more suited to him.
Others may be able to assist further.
Cheers
Waylander