Watch List notes:

Commemorative Medals, British Historical Medals, William IV, The Opening of London Bridge, Silvered-copper Medal, 1831, by Benjamin Wyon, head right, rev view of the bridge, 51mm. (BHM 1544; E.1245; W.1). Very fine, but patchy tone.
The medal was not struck in silver, however the plating to the present medal looks to be official. (60 - 80 GBP)