This mark appears on a small number but significant number of buckles with the Lion Passant Guardant of 1756 —1784. I have never seen it on one with a duty mark.
These examples are from
Shoe Buckle Knee Buckle
Silver Gilt Knee Buckle Stock Buckle
There are two strong candidates for this mark Benjamin Cartwright and and Benjamin Cooper II .
I have examined the copy registers at Goldsmiths Hall and although I felt Cooper was the more likely, I found neither of his recorded marks, Jan 1764 (Grimwade 141) and Sept 1765, matched the marks shown above
Both were working pre 1758 so either could have a smallworkers mark or marks in the lost register. Both were involved with bucklemaking . However the styles of the buckles bearing these marks all appear to be pre 1775 so perhaps Cartwright, who died in 1771 has the better case Benjamin Cartwright
There were at least two Benjamin Cartwights, which both Heal and Grimwade (and I think the PR1773) struggled to separate. Knowing that one died in 1771 enables more sense to be made.
Benjamin CARTWRIGHT I -Probably free of the Blacksmiths and entered an incuse mark as smallworker at 3 Horse Shoes, Pedlars Lane , Cow Cross in 1722, and a largeworkers mark at Crown & Pearl , Bartholomew Close in 1739
Further marks there in 1748 and 1757. In 1758 William Tant, son of William Tant buckle- carver was turned over to Benjamin Cartwright, Blacksmith (who was probably free of the Blacksmiths)
In 1754 Benjamin Cartwright II ,described as "Junior" entered a largeworkers mark , Smithfield. His subsequent marks were at Kings Arms & Snuffers in the Strand, 1756 and Paved Alley, Pall Mall) in 1770, where he appears without category in PR1773).
A Benjamin Cartwright, presumably Senior, was fined for substandard buckles in the 1763 - 1769 period.
In 1768 the Proceedings of the Old Bailey Ref: t17681019-11 reports a Benjamin Cartwright, again presumably Senior “ I keep a silversmith's shop in Smithfield…… I had two dozen and two stock-buckles in my shew-glass, and when I came to count them, there were only seventeen remaining”
On 15 June 1771 the Will of Benjamin Cartwright , Goldsmith of St Bartholomew the Great, City of London proved at PCC
According to Grimwade Benjamin Cartwright I also appears in the PR1773 without category at Paved Stones, Smithfield but this seems to be a confusion with his son by the writers of the PR1773. Paved Stones and Paved Alley seem similar Benjamin Cooper
Grimwade records two Benjamin Coopers (I and II) but speculates that although their signatures differ they may be actually the same man. The report in Gentlemans Magazine of his death in 1786 at the age of 88 mentions that he had been a working silversmith for over 60 years . This certainly suggests one long lived man, with his son Joshua succeeding him at Brownlow Street Holborn
The Proceedings of the Old Bailey Ref: t17600416-33 on 6 April 1760 reports Benjamin Cooper as stating . “I live in Brownlow Street, Holbourn, and am a silver-smith. The prisoner was employed to file silver buckles for me,” This case also indicates that his son, unnamed , was also either a youth or an adult at that date
He was fined for substandard buckles in the 1763 —1769 period and appears in PR1773 as a bucklemaker.
Gentlemans Magazine 1786 page 910 records under deaths " In Brownlow Street, Mr Benjamin Cooper aged 88, upwards of 60 years working silversmith ".
The Will of Benjamin COOPER, Goldsmith of St Andrew Holborn was proved at PCC on 17 October 1786
On the same day Joshua COOPER registered a bucklemaker mark at same address .