April Yates, trading as Feather and Frost, is registered with the London Assay Office.
Hallmark stamps are applied to all sterling silver items weighing over 7.78g in accordance with the Hallmarking Act 1973
Items under 7.78g are not routinely stamped. (Excluding the weight of the stones and separate chain)
Items consisting of/containing gold are stamped regardless of weight with either a part or full mark.
https://www.assayofficelondon.co.uk/media/2943/dealers_notice_b-221021.pdf