This is a very rare Archibald Knox silver "Cymric" brooch designed for Liberty & Co. It is in the form of a Celtic or Romano British fibula, stylised zoomorphic and foliate design, stamped marks, 4cm long.
Photographs and description (in part) by Kingham and Orme auctioneers and a private collector.
Additional note:
This brooch is shown on a card collection in the Manx Musuem which was taken from Archibald's residence after his death. An image of the card is shown below,
On looking through the Liberty & Co. jewellery sketchbook this brooch has the model number 1223.