Thanks for the image Miles.
Cannot help with identification although I suspect it may be one of the William Coles.
There are almost certainly two William Coles.
One was still alive in 1764, and the other retired or died around 1754 leaving his business to William Harrison
Grimwade gives one (which could refer to either of the above Coles) as son of Joseph Coles, late of Ovinge in the County of Buckingham,tobacconist deceased who was apprenticed 9 August 1715 to Abraham Pope of the Leathersellers. Pope was also the master of Robert Elliot , another bucklemaker, who was in turn the master of Samuel Eaton, who was in turn the master of George Smith II of Huggins Alley/ Lane . (Grimwade has conflated two separate silversmiths under George Smith II in his biographies )
First mark entered 5 August 1724 as smallworker in Shoe Lane . An important road , it ran N - S from Holborn to Fleet Street. Again this could refer to either of the Coles.
The evidence of insurances and Poor Rate and Land Taxes records indicates that one William Cole was working in the parish of St Michael , Wood Street, almost certainly in Huggin Alley from at least 1734. He appears to have moved to Monkwell Street in St Olaves, Silver Street around 1741, and his Huggin Alley premises were taken by Samuel Meriton. This is almost certainly the William Coles that Heal records as Silversmith , Silver Street, St Olaves in 1744. His premises at 38, Monkwell Street were taken by William Harrison around 1754 and he was almost certainly the man from whom William Harrison obtained his business
The will of William Coles of Saint Martin Vintry London proved 18 July 1750 is not relevent - I've checked it !
In the card files at Goldsmiths Hall are several slips of paper from the Guildhall Library which give details of insurance policies referening to Goldsmiths or Silversmith
Two refer to William Coles.
1727 William Coles Silversmith, Huggins Alley in St Michael, Wood Street. House Â£300, StockÂ£250, Linen etc Â£50. Total Â£600
1742 William Coles Silversmith, Mugwell Street in the Parish of St Olaves ,Silver Street Furniture Â£100, Goods Â£600, Total Â£700
I think this mark could well be the William Coles of Huggin/Monkwell. Dates fit nicely.
The other William Coles was still alive on 19 January 1764 when his son William was apprenticed to him, The son was made free 1772, so perhaps there are three!
I have a stock buckle, also with the London Lion of 1740 -1756 with what seems to be the same mark. Bucklemakers often made cast tongs.