Unusual Strange Solid Mini Brass Tank. Lot # 486

Description

This mini but serious looking brass tank amazed me for all the years I had it. It is a
conversational piece
in my home. But it is time to let it go!
I have no idea what it is? It has 2 black handled valves. One controls flow of something, perhaps steam through an angled discharge tube. The second valve seems to shoot steam through a whistle pipe. On top it have a large round fill cap which I was not able to open. Actually, I don't know if it is openable or it is in fact a fill cap?  Also on top it looks like it has a pressure relief valve?
I appreciate it
if someone could ID
this item for me. At this time I will offer it at a price worth having it as a conversational piece!
I did not polish it because it has a beautiful patina.