I looked at that the other day. It's definitely not original. The butt plug, while fairly nice, is wrong as the originals don't extend that far from the butt of the horn and the turning on the originals doesn't show turning marks and the chip carving is much neater. The screw tip is also wrong as it doesn't follow any of the patterns used, the thread seems small - should be 5/8 -11 - and the base of the tip should be larger in diameter - after all it's meant as a funnel to use in filling the horn. The paired lines on the horn at either end should be deeper, they're nice cuts on the originals, not faint lines. Art DeCamp, who is the expert on these things, showed me at the CLA show that the only numbering on originals are some Roman numerals scratched on the square shoulder of the horn body at the base of the threads and on the base of the screw tip. These might be IX, or XXI, or some such. The highest number Art's seen is less than 50. Apparently the horns were made in batches and the numbers were put on to make sure the correct tip got on the horn at some later stage in the making. The one on ebay doesn't come close to the quality of horns of this type made by Art. The one on ebay should sell for just about $100. A really first rate copy by Art of one of the few other guys who can make these virtually identical to the originals is about $350. The tips on the original York horns are all horn.
Tom