I believe this was issued in commemoration of the Relief of Mafeking during the Boer War of 1899 to 1903. No military connection but the sort of civilian medallion sold quite commonly in the early 20th Century. It probably had a patriotic red, white and blue ribbon. Similar items were produced for royal weddings, funeral, coronations, etc. Not limited to medals this sort of commemorative would also include, tins, flags, tie pins, coins, etc.