I think you have a Gaelic inscription "Doire Feis" or Derry Feis. A feis is a traditional Gaelic arts and culture festival.
The Derry (or Londonderry) Feis is quite famous, the first took place in the Guildhall in April 1900, its competitions were open to entrants from all over Ireland.
I think this is a medal from competitions for this festival, possibly even the first or second one (1900/1901) given the crown.
http://www.irishnews.com/news/northe...y-feis-470088/
A quick internet search (cached images) show the medal descried as such.
John