the leftovers of my last oil-change contained swarf, chrome, gasket sealer and a fly.

btw: only one rocker needed doing and the motor is still going strong!

Many moons ago when I changed the oil screen on my old DR750 (no really), I found a complete cam chain tensioner, in bits, resting in the bottom of the engine.

I checked, and there was aonother one up top tensioning the cam chain.

Spin

Anything curly is generally machining swarf. But any con rods, bearings, gear teeth etc stuck to the magnet could mean significant wear! Look out for holes in the side of the casings or barrels accompanied by difficult starting with probably a dark liquid (almost oil like) in fairly large quantities inside the fairing, around the engine cases and on the floor.