That 'tip' is the wire-wrap bit.
There are different sizes depending on what size wire you're using. The bits can be
pretty expensive, so it's good that you have at least one of those with the tool.
(The tool will be able to accept other size bits that whoever gets it will be able to buy).
The tool is expensive, but don't get your hopes up too high about making a profit on it,
because there just aren't that many people that use them any more.
(If you DO find other bits for the tool in your search of what your Uncle had, keep them
with the tool. They'll look the same, the size of the hole in the tip will be different).
Good luck if you try to make some money off of it for your aunt.
Oh, there aren't any other parts to the tool. Just the interchangeable bits.