In what year was the first can opener invented?

The can opener wasn’t invented until 48 years after the invention of the can.

A can opener (in North American English and Australian English) or tin opener (in British and Commonwealth English) is a device used to open tin cans (metal cans). Although preservation of food using tin cans had been practiced since at least 1772 in the Netherlands, the first can openers were not patented until 1855 in England and 1858 in the United States. These early openers were basically variations of a knife, though the 1855 design continues to be produced.

Dedicated can openers appeared in the 1850s and were of a primitive claw-shaped or "lever-type" design. In 1855, Robert Yeates, a cutlery and surgical instrument maker of Trafalgar Place West, Hackney Road, Middlesex, UK, devised the first claw-ended can opener with a hand-operated tool that haggled its way around the top of metal cans.