I don't recall ever seeing a Briggs from that era that had the air cleaner housing a different colour from the cooling air cowl, so there seems to be reason to suspect your air cleaner is not original, or has been repainted. The parts list shows that the 110900 engine family came with both types of air cleaner. It does not show either type as applying to particular Codes, so it looks as if it may have simply been one of the features the buyer (that is, the mower manufacturer) could specify. If that is the case, the Scott Bonnar catalogue is probably the best available evidence.
I suggest you send a PM to Deejay, who has access to some of the old SB data. He might be able to figure it out. If he has nothing, my guess would be you have a 520081, and it should have a snorkel. Possibly the previous tenant wanted a snorkel set-up for another mower with a Briggs engine, so he swapped them over. That would explain why the air cleaner is the wrong colour.
