So, the material of that thingamajig, impeller, propeller, magnet, is that rusty steel, or brown plastic (bakelite? does that still exist?), or something else?
The worn-through shiny coating is not a deposit any of my beers would leave, I'm pretty sure about that. To me it looks more like a thin aluminum or stainless or tin cover that the manufacturer put there. It looks like it has chatter marks (vertical lines) in the lower part, and is worn through near the top. So my second question is: why? Why is there a thin apparently not too abrasion resistant cover over some other material?