I recently bought some aluminum corners and sheets of aircraft grade aluminum from some guy. He assured me that it was real aircraft grade aluminum.
Alex, 'aircraft grade' could mean almost anything. The alloy properties like strength, density, modulus, heat treatment, extruded/rolled/cast/forged/weldability... and price have a big say in what the component will be made from whether its a door hinge or critical engine mount. If you got a good deal & are happy for your application then that's all that matters. But just know that usually people source & compare based on a defined alloy. Here are some common ones but I'm sure a more extensive list is in the hundreds.
https://www.aircraftspruce.ca/menus/me/aluminum.html