This medal was instituted in 1847 and issued only to surviving claimants in 1848. It was awarded to cover engagements of the French Revolutionary and Napoleonic Wars (1793-1815) and the war with the United States of America (1812-1815).
Note that this reproduction bears the Badajoz clasp which was issued only to those men who participated in that battle in 1812. A total of twenty-nine clasps were sanctioned and according to the Wikipedia the maximum awarded to any one man was fifteen. The medal was not issued without a clasp.
Also note that there is an authentic MGSM displayed at Panel 22. It was issued to a 'D. Macpherson' and bears the Martinique clasp (1793). Although it is displayed in connection with Duncan of the Kiln (our 19th Chief) it is unclear who the actual recipient was.