A while ago I found a powder flask and today clearing off the bench gave it a shake and this came out
That’s one of the gates used to measure out the charge. Usually a couple in the spout
Must have been in an upright position and fallen in as things broke up. Nice twist .
I had to look twice at it before I realised that it isnt a shot flask cut off. I agreed with mudwiggle initially and then realised that mudwiggles picture is of a shot flask and the see saw arrangement gives the exact measure of lead shot and your find is not a shot flask but is a powder flask so your small attachment is the broken of cut off for the powder. In its own right it is not broken but it is the internal section of it and the knob at the end goes through the body of the flask to attach to the spring loaded finger lever.
you can see the little device closing off the entrance to the flask and the spring operated lever that activates it in the photo.