Brooch with backward looking beast, 9th C, 30 mm, with backward-looking beast, Yorkshire.
A very similar brooch was found in excavations at Jorvik, York, Yorkshire.
This type of brooch has been most commonly found in East Anglia. Rarely this design is also seen in art from the Baltic Viking settlements. I think these beasts are modelled on a Byzantine lion motif.
A number of examples are recorded in the PAS database. "Copper alloy Plate Brooch. Cast discoid plate bearing the image of a backward facing beast with jaws agape in low relief, with a billeted border. The back retains the stubs of a pin seat and catch plate, suggesting the pin to have been roughly aligned with the beast. Abraded. This is a common type, described by Hattatt (1987), page 315, fig. 103 nos 1310-1311) as a 'poor man brooch': a useful indicator of the Viking Age settlement of ordinary folk. Suggested date: Early Medieval, 850-900."