Hello and nice finds. I think what you have found is the top to a stanchion post (think the velvet ropes they had in the old theaters, carnivals, circuses, etc. for showing where the lines formed) If you search " brass stanchion posts and ropes" and look at a few images you'll see what I mean. They have been used for a very long time (at least a century) and some remain little changed today. It looks like some areas of the surface had a little less corrosion, if you look and see if there is clear lacquer that would date it a little later. The brass bed knob could be the right ID but those were usually a little lighter. A doorknob sure cant be ruled out but it would have needed an insert to mate with it's spindle, it's possible that corroded away but the open part of your find does not look like it's too heavily corroded like you'd from dissimilar metals. Very nice save and Happy Hunting!
