Sounds like one of those awesome mechanical kitchen tools from the days when appliances were built to last!

Based on your description (aluminum, round, grooved, and rotating), it’s most likely a specialty can opener or food grinder, but it’s also more likely:

A classic wall-mounted can opener (or a handheld model with a cutting wheel).

In old kitchens, can openers were often made of solid cast aluminum. The round, grooved part is a transport wheel.

How it works: The grooved wheel grips the edge of the can. By turning it (usually with a knob on the back), the can is guided around the cutting blade.

Why aluminum? It was lightweight, rust-resistant, and easy to cast—ideal for postwar kitchens.

Alternative: A skewer attachment or berry grinder.

If the tool is more funnel-shaped and the grooved part is on the inside:

It could be a food mill (for jellies or sauces). The grooved, rotating part forces the soft food through a sieve. Aluminum was often used for this purpose before stainless steel became the standard.

Third option: A nutcracker.

There are old aluminum nutcrackers where you put the nut in a recess and the grooved wheel is tightened over the thread to crack the shell in a controlled manner without damaging the kernel.

To be precise: Does the tool have a sharp edge or a small wheel with a sharp edge? Or does it resemble pliers with a round handle?

A little tip for aluminum finds: Please do not wash them in the dishwasher! The harsh salt causes oxidation of the aluminum, which turns it black and discolored. A soft cloth and a little detergent are the best way to restore its original shine.

Can you describe whether the wheel has teeth or rather fine grooves?