New Old Stock (NOS) Mohawk alternator belt tensioner, part # 23533015, compatible with Detroit Diesel Series 60 engines in buses, trucks, and heavy-duty diesel vehicles. Made aftermarket equivalent part is unused, in original sealed plastic packaging with minor box wear. Metal parts like gears have grease on them, this is not rust as some pictures my seem to show. HIGH-VALUE / SERIALIZED DIESEL PART? Clear evidence of part swapping or fraud? Honest mistakes or fitment questions? Happy to work it out!