I believe the other marks are for London 1735, found on a toddy ladle.
Thank you

silvermakersmarks wrote: Sun Jul 09, 2023 1:10 pm This mark hasn't been recorded by Grimwade. There is, however, a BC mark in his "Unregistered Marks" section. It is shown as BC in conjoined circles and noted as seen on a 1734 brandy saucepan. As it was taken from a real-life example it is possible that the original was actually the same as your mark and was mis-drawn. Grimwade further suggests comparison with 2 marks of Benjamin Cartwright II which do in fact closely match the form of your mark. These marks, however, were registered in 1756 and 1770 and there is no firm evidence of Cartwright working before 1740.
So, no definitive answer I'm afraid.
Phil