Blizz,
The accuracy of my measurements is due entirely to the fine quality of the images in The Antique Phonograph.
I'll be sure to mention the part about the gold to my wife...
It really appears to be a Coin op horn. I have a Columbia BS that came with the original nickeled brass similar horn. Yes, the horn does slide over the elbow. I just measured mine and the horn is 12 ⅝" in length and 7" diameter. I measured the small end with calipers, the i.d measures .745" and that inner sleeve is .750" in length.