Noticed several queries on this thread appear to have gone unanswered.
The list of Royal Navy, Royal Marines QSA recipients is available online at www.angloboerwar.com
, those who served on HMS Gibraltar are on http://www.angloboerwar.com/rn_ships/gibraltar_qsa.htm
his entry is given as
Thome, Ordinary Seaman F G. QSA (0)- the zero indicates no clasps.
As there are no RN records for anyone named Thome at http://www.nationalarchives.gov.uk/documentsonline/navy.asp
it must be a transcription error and he's the man whose medal you have.
Searching the RN seamans' records on the National Archives site for fr* thorne shows 3 records for the Thorne surname that would have initials FG - you'll have to purchase and download the records to find out which served on the Gibraltar.