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I believe what you are referring to is known as a side can opener or a smooth edge can opener. You can find them and purchase them on the internet. They were designed to eliminate sharp edges to reduce the possibility of cuts. Food should not be stored in opened cans. Do not use the lid to cover the can for storage.
smooth
Willow leaves are smooth-edged.
its cleavage
A nickel has a smooth edge. No ridges.
its cleavage
A crystal!!
A crystal
It is a general-purpose bench plane used to smooth wood -- frequently to smooth the edge of a door that is sticking.
I have a Canadian Dime 1980 with smooth edges too but have no idea how much it is worth
polyhedran
A can opener opens "tin cans" (though they do not contain much tin now in the manufacturing process).A metal can opener first punctures the lid of the can, then is manually clamped down onto the lip of the can. The lip is the raised edge around the lid. The manual opener then works from a human turning a wheel on the opener. This action begins to "cut" the metal on the inside of the lip / outsider edge of the lid. The opener contains a magnet that attaches to the lid, so when it is completely cut, the lid can be lifted off. The edges of the lid may be ragged; it can cut skin. The lid is thrown away; the food is removed and the can is thrown away.An electric can opener operates on the same principles: using a lever, clamp, magnet, wheel, and a turning action. The main difference is less work for a human.Some men or military personnel use a knife with a second edge on it. This uses manual force to puncture the lid and to go around the lid. The edge is very jagged. A knife carries more risks.