Spike, just one more question; when you pull the two halves apart so the edge of the larger half meets the flair on the bottom half, is the pin flush on both sides of the whole thing, or does it still extend beyond the whole deal on both sides?
You usually guess these things Spike and I see why you're stumped. A float seems unlikely,as water would get through at axle hole. A wheel seems most likely, but to what? The only toy wheel it would seem to fit with this kind of axle arangement would be a steam roller, but this is narrower, and beside, most toys were made of tin, not brass.
spike, it's a one in a zillion long shot, but some of the old 19th century pull toy boats had a wide wheel hidden underneath so they could be pulled along the floor as well as floated. Don't know if these were ever made of brass or copper though...
If the piece through center is a hollow tube, just filled with dirt, I would guess float from old S.U. carburetor. All seams would have been soldered .