Sentences with Back Number

My little sister found my old CD player and called it a back number gadget from the past.

The dusty encyclopedia set in the library is filled with back numbers, with information that is no longer accurate or relevant.

The weathered treasure map discovered on the pirate ship was a back number, leading the adventurers to the wrong island.

The black-and-white photographs in the family album are back numbers that provide a glimpse into the generations that came before.