Edinburgh was the main Scottish Assay Office. Edinburgh’s marks consist of:

Maker’s mark
Town mark, (three castles)
Thistle
Variable date letter
Duty mark, (from 1784 onwards)

The rules were not always strictly followed when it came to hallmarking sugar tongs. Either the thistle or town marks were used on a fairly random basis.This means that a pair of sugar tongs could be marked with either the thistle or the castle, but rarely with both. The date letter was not used until quite late. Very often multiple marks are punched, either the maker’s mark several times or the thistle. This is even more noticeable with the provincial towns. There were a number of Edinburgh makers and I have shown tongs by them below.If you are looking at collecting Scottish Provincial work, bear in mind that it will often be hall-marked with Edinburgh marks.

We also know that there was a massive fire in 1796 which destroyed their duty registers, although some older records were saved because they were kept separately by the deacon. We therefore only have duty registers from 1799 to date (less 1805 - 1811 where the register has been lost). - Many Thanks to Robert Wilson for this information