Simplify the following text for a Grade 11 native English-speaking person.
Original: Bell 's instrument is a 300-year-old Stradivarius violin called the Gibson ex Huberman , which was made in 1713 during what is known as Antonio Stradivari 's `` Golden Era . ''
Simplified: Bell 's violin is a 300-year-old Stradivarius violin called the Gibson ex Huberman , which was made in 1713 , a time when Stradivarius was making his best instruments .