Packing food in cans has been practiced for a number of years and predates the invention of can openers by quite a bit. The first cans were invented in Holland and boat provisions were packed in iron cans that were tin plated. Once sealed it was actually very difficult to open them and even the instructions on the can said "Cut round the top near the outer edge with a chisel and hammer". These cans were very robust containers and often weighed more than the contents themselves. These were known to be used at least since 1772. It was however only in 1855 that the first can openers were invented.
The earliest can openers were little more than a knife with a lever that worked against the edge of the can. These were very simple designs and are in fact still in use as a very basic manual can opener. In fact you can find these lever type can openers in key-chains, penknives etc, even now.
Variations of the same basic design have been introduced and have both succeeded and failed. The second distinct kind of can opener, the rotating wheel kind was invented and patented in 1870. The initial design was not very successful because it had a long lever which had to be pierced into the center of the can top, and had a rotating wheel that had to be pressed down by hand to enable it to cut. This kind was not very successful and would have fallen by the wayside had it not been for an upgrade to the design that had two wheels that enabled the user to hold the opener tightly against the rim. This design was so successful that it is still in regular use even today.
After this a number of other designs, principally the electrically operated can openers, came up and have been met with varying degrees of success. In the 1930s the bunker type of can openers that had the grasping pliers kind of grip that both held the can and cut along the edge were invented. This model forms the basis for all other can openers today. It is in itself only a slight variation of the double wheel can opener, but was easier to use and was therefore preferred for everyday use.
Today, there are many more different kinds available, starting with the one touch can opener, to the "lids off" jar openers that can open the lids of almost any kind of can. All of them are efficient because they all use the same principle, it is just your preference on what kind you prefer.
