Off my 1976 K10 Chevy truck with a 350 4bbl. In service for 2 years and a little shy of 2,000 miles. First oil change since I had the oil pan off to install a new oil pump due to a weak bypass spring in the factory pump bearings looked good when i had the pan off. Engine isn't rebuilt but is not original to the truck however it is from a 1976 passenger car according to the stamped pad on the block. Truck sits a lot due to other commitments and not being my daily driver.
Found some carbon as shown in the pleats and some gunk settled out on the bottom of the can but nothing ferrous or scary looking.
Oil in use was Mobil Delvac 1300 15w40. Napa 15w40 and another PF35 went back in and on. Enjoy.