It looks like all brass??

Sorry, but I don't understand your question.  From the photos the bell looks silver.  That is in contrast to the brass key guard.  King was known to be producing horns with sterling silver bells and necks in the late 1930s, which makes me wonder if you have an example of that theme produced earlier than is generally known.  Maybe some additional pictures of the whole horn, including the neck, would be helpful.  There is also the possibility that the bell is silver plated.  Maybe inspecting where the bell toneholes are attached would yield some clues as to whether it is sterling or plated silver.  Or you could have the horn inspected by someone who really knows their silver to determine that.

I guess it could be silver or silver plated.  I was a clarinet player.  I really don't have knowledge on  saxophones.  that's why I posted on here. thanks.