Yes, it is a Jubilee medallion. The jubil;ee was 1937-1887. The head design is the special jubilee small crown, similar to that uiused on coins from 1887-1892.
I beilevbe, from back in the depths of my memory, that J W Ellis was a jeweller of the standard of Birks now- they did make such commemorative items for themselves and others. The Jubilee was a huge celebration in England. The portrait is a lot older than the ones on the coins.