Looks like the original Aqualift brand muffler was replaced with a Vetus Waterlock brand muffler. Vetus makes very good products so I'd consider that an upgrade.
For cleaning, at different times I've had success using Barkeepers Friend, Simple Green, TSP, FSR, and distilled white vinegar mixed with dish soap (1 teaspoon of white vinegar and 1 teaspoon dish soap per cup of water).
For cleaning, at different times I've had success using Barkeepers Friend, Simple Green, TSP, FSR, and distilled white vinegar mixed with dish soap (1 teaspoon of white vinegar and 1 teaspoon dish soap per cup of water).