Unknown monument Bishops Castle

We visited the delightful market town of Bishops Castle today and came upon this plaque or monument I'm not sure what to call it. It is dated 1781 has an elephant on one side and a gryphon on the other with latin words on it -' tria juncta in uno' three joined in one. The three joined in one can be a reference to the Christian Trinity. I'm wondering if it has anything to do with Clive of India who bought a lot of estates in the town at that time. See history below:

During the eighteenth and nineteenth centuries, Bishop's Castle became one of England's notorious "Rotten Boroughs". Votes of "free" men, the burgesses of the town, were bought to ensure the election of candidates supported by the land-owning classes. Such bribery ruined the Walcots. In 1763, their estates were bought were bought by the wealthy Clive of India and from then on, the Clive family controlled the constituency of Bishops Castle and its elections until the Reform Act of 1832 which deprived 56 Rotten Boroughs, including this town, of both their Members of Parliament.

I think we need to revisit when the museum's are open. It seems a fascinating place with lots of walking in the area, an interesting history and several pubs, two of which brew their own beer.