I did a 3000mi cleaning phase on my 200k BMW M42 motor in an attempt to quite the valve-train noise. I inspected the oil filter after the 3k oil change and found what looks like shavings... about the thickness 90min audio cassette tape. I can't tell if they are copper shavings or flaked off oil deposits.
I'm not sure if this is from the cleaning or if its a rod bearing about to let go. (sorry for the picture quality) Has anyone seen such debris in their filters? I searched here and found no mention of this type of debris as the result of ARX.
It does not look like metalic particles at all. It may well be debris that let loose from the oil pickup screen down in the pan. Sometimes piston ring deposits can be freed up in tiny granular form, which have been seen in filters before.
What is going on with valve noise that you are looking to correct?
See if it crumbles under pressure or additional manipulation. Frequently carbonaceous particles of this size can be found in filters. They're usually described as "grit", in that they crumble when rubbed together.
This doesn't discount the notion that they're composed of some bona fide engine material. It just wouldn't be the result of Auto-Rx other than if it was entombed in some deposit formation and then liberated.