Detroit Diesel Series 50 oil pump assembly, box part number R23530487 (stamped 23530486 on unit-variant with no functional difference). Balance shaft, high-flow design for 8.5L engines in buses and trucks. Remanufactured to OEM standards by Detroit Diesel/Reliabuilt. New old stock (NOS) in original packaging, unused. Metal parts like gears have grease on them, this is not rust as some pictures my seem to show.