A very interesting little item indeed, and one which we don't ever recall handling.

The small base just below the bust of Wesley and the bust of Wesley itself are cast in what seems to be iron. The bust and small base portion of the present matches almost identically the 1839 wax seal bust of Wesley that was produced and widely distributed for the Centenary. The only difference being that the back of the smaller base does not read "1839." And the wax seal was carved from black horn rather than cast. 

The 1839 model described above was then apparently combined with a larger base [apparently at casting; we see no indications of a weld] to make a free-standing all-iron bust. Produced around the same period and probably American. 

The whole is very effective with some patination and handling and light oxidation. A very slight tilt. Measuring approximately 5 inches in height, but of significant weight due to composition. First-rate.