How do I get rid of all this brown on the brass?

Thanks a bunch @Pharael !

 

@Remus1956 Thought you'd have a good reason! Great work, some of these old ones take a lot of gentle effort but always worth it in the end!

 

@Blackdog I was really nervous to overheat the brass and cause stress cracks....haha.... You should have seen me muffify the stove with wet paper towels.
@Pharael spotted a cast iron trivet that was on tradera so I'll be bringing this one back to life for sure