Vortecd guessed first so he’s the winner!!! Yes, it’s the blower drain plug! (No you didn’t win my blower lol)
I’m surprised it was not equipped with such, the IHI has 4 magnets in it, both fill and drain and also a circular ones in each bearing oil supply port and they even polarized them opposite of one another. IHI must have been concerned with metal getting into the bearings for sure, GREAT oil system in the IHI blower. Maybe some day I’ll see how Whipple is doing it. Maybe they have magnets some where in there. One of the reasons I like magnet so much is it gives you an idea if there’s any contamination going on (wear) because it collects the debris for inspection, then also it captures it to prevent it from doing any damage but it’s like instant oil analysis without sending it out.