Backstory here: I picked up an 85 B250 from the original owner who was/is a ME and was pretty thorough with preventive maintence and just in general took very good mechanical care of things.

I dropped the oil pan to clean out the trash that got flushed down from doing a manifold reseal and do the rear main as well. Without going into the records (like looking through a phone book he noted everything he ever did ) I know the engine was overhauled sometime in the late 90's (rear main bearing lower shell said 3/98 on it). There was a HUGE magnet stuck to the bottom in the sump. At first I thought it was something he added but once I wiped the sludge layer off there was the very faint remains of a part number stamped on it and the pentastar logo on it as well so its certainly an OEM part.

looked through the parts books and can find no reference to it. part number is not legible at all. Never seen such a thing from an OEM before ?

I have found them in Torqueflites, in the pan, around the dimple near the dipstick tube area, can't recall any markings, but then I wasn't looking very hard ... just wiped them off and re-installed.

Shaped like a thick washer,IIRC.

For scale the top/bottom surface area is roughly the shape and size of a credit card. probably weighs 3-4 pounds ?

So nobody has ever seen such a monster before ? I'll be dropping it back into the pan this evening and hopefully firing up the engine this evening if the planets and stars align. fingers crossed theres no damage from sitting for the past 4 months.

Pretty obvious that someone added it.