Complex sentence: The collection is significant because it includes the first induction coil which was invented by Callan and a number of his other induction coils, including his giant induction coil (pictured) which he invented in 1845.
Split into simpler sentences: The collection is significant because it includes the first induction coil. There are a number of his other induction coils, including his giant induction coil (pictured) which he invented in 1845.