The clasps will generally signify a battle he was involved in. It was customary for a medal to be awarded to all participants in a campaign, e.g China War medal. This would then come with clasps signifying the battles participated in, e.g Canton, Taku Forts.
Are you sure it's not LC badges as well? I know the marines used to award GC badges on a regular basis, note they really were badges rather than medals.