I'm pretty sure that's a stir bar.
I was reading up on Alnico (Aluminum, Nickel, Cobalt)stir bars from the 40s. They will lose their magnetism if stored improperly. Back in the old days they were stored in pairs, end to end to avoid losing their magnetism.
Alnico stir bars have "high heat resistance but very low coercivity. This means they require reletively little energy to lose their magnetic alignment."
In the 1940s, it was common to store them in pairs north to south. Storing them alone allows the magnets's own external field lines to loop back and slowly weaken its own domains over decades.
Dropping them or causing a physical shock "disrupts the magnetic domains out of their aligned state".
Storing them in a junk drawer or jumble of metal objects exposes them to stray magnetic fields over decades. "Without paired storage, individual domains drift into random , entropy-favored orientations."
