I thought about this and it makes me unsure ... Would metal spools and cans harm the magnetic stripe? After all. It is magnetic and metal (perhaps not aluminum) attracts magnets, right? Any info that will put my unease at rest appreciated)

Erm no. Going off that logic there Vidar, no projector would contain any steel parts, which of course they do. To avoid accidental erasure simply keep those tracks away from any strong magnetic source at close proximity, but near metal (ferrous), all should be unaffected.

Never forget, your transformer relies on magnetic fields to transfer voltage from the primary winding to the secondry (s).
If this has no effect on the delicate stripes, I think we can rest assured metal reels and cans are ok.