Copper alloy penannular brooch.
The terminals of the brooch are bent round back on themselves and are decorated with two small grooves. The freely moving pin is flattened at one end and looped around the brooch, it then becomes circular sectioned and tapers to a point at the opposite end. Both the surface of the brooch and the pin have been gilded.
Similar brooches are shown in A Visual Catalogue of Richard Hattatt’s Ancient Brooches (2000), dating from the 1stC BC to 1stC AD, p340.
A more precise example; Hattatt Ancient and Romano-British Brooches(1982) No. 117, which dates to the 1stC AD.