I would imagine it was just a conventional 10W30 or straight 30 oil with some extra moly mixed in. It's not a requirement, but most OPE takes something on the order of a quart or less-pretty cheap insurance if you ask me! I can't believe the newer Briggs engines have LIFETIME crankcase fill-they aren't betting on tightwads like me running one 20 years or until the deck rusts off...
Briggs and Stratton uses a lot of plastic in their engines including the camshaft. Lifetime might have a different meaning from the older engines.