Interesting stuff here 56,
First off, all the swarf in yours looks pretty benign. I've worked on compressed air systems,hydraulic systems and automotive/bikes for nearly 40 years and religiously open any filter after the first service. In all that time I've only seen 2 or 3 that gave me any concern and only once was it a complete mechanical failure (factory left out bearing shim pack on a rotor) and all kinds of shiny glitter in that filter. Those filters do a remakable job and it's hard to say what some of those pieces are without an electron microscope.
Like you say probably bits of gasket,sealer,oil dry or Guidos lunch crumbs.
Paul B :BEER: