Thank you nobilityhouse and agphile. I am amazed to see the collective knowledge here. To be honest, I have been working on agphile's lead (Carter) and still couldn't figure it out (checked a few books on archive.org on heraldry). The complete attribution provided by nobilityhouse is simply awesome....
Thank you. I should have also mentioned that this is stamped along with other hallmarks that trace the item to 1763 London Assay Office (see pic below). Also, I think it's not a Lion but a dog.