Victorian (1865 ) Celtic Revival Bog Oak and Silver Gilt Brooch/Pendant

On the road today catching up with family pre-Xmas and stopped at a favourite country collectibles store.

Saw this brooch/pendant in a bit of a grubby state then realised it had a Victorian Registration Lozenge.

Overall size is about 45mm square, the four panels are about 18mm square. When I looked at it more closely I saw the extremely fine Celtic interlace carving on the four bog oak panels. The detail is so fine that at first I wondered if the panels were moulded in vulcanite or gutta percha.

However when I looked up the registration mark I found the top mark (II) designates the class of "wood" and the hot pin test confirmed it. The date from the lozenge reads 7 March 1865 which is the year there was an International Exhibition in Dublin (International Exhibition of Arts and Manufactures), so maybe this was an exhibition piece or souvenir?

Celtic Revival pieces float my boat so of course this came home with me. I'd love to find out who the maker was, it must have been someone significant to go to the trouble of registering the design, any further info will be gratefully received.

Will add a link below in first comment on how to interpret British Registration Lozenges.