Correct the powder did not dissolve in water. Did not discolor anything either. I tried mixing it pretty good as well. If it was a pen holder it would make for a very heavy pen. That brass "handle" is uncomfortable to hold like a pen.... but it is possible. It looks like the tube was put in and then the base was sealed onto the bell. Would explain how it got into the object.
It does not ring any any way. Unless a "thud" is a ring. The powder is VERY plentiful inside hard to tell how much though.
Xrays I believe can penetrate brass, should be able to make something out when comparing brass to brass in an xray. Where as the xray vs a person will not be as powerful.
I have tried to unscrew the tube with the knurled ring off. But it just spins forever and does not tighten or loosen in any way.
*edit*
I was thinking, if this was a quill pen holder... would they really be making them AFTER 1945 ? Since that is the date range for that peerage stamp...
Still strange, wonder if I will ever know for SURE what this thing is.
Ill try to go back and edit the first post with modified information when I have some extra time to sit down in the next day or two