I saw with satisfaction that you won it and I was about to ask you what's up.
Exceptional horn indeed. How old is it? 50, 60, 70??? Assuming that there were Leslie's copies of this horn before WW2, the serial N° just gives us an idea of its age.
This intergrated valve fooled me. I have been mislead the seller's pics, I though the horn's throat had been half sawed off!!!
This is really great to find such a horn in its developping process. You must feel like if you had found an old steam whistle!!!
And sure you were lucky too to pay such a price!!!
This horn is very similar to my Tyfons 75 & 200, same shape, same power chamber and back tab, same bell...
Just like your 425 DVE comparison, there is certainly some ratio to calculate to get the correct size between the different models.
I have added a few pics from my own horns.
Tyfon 75 002.JPG [ 407.56 KB | Viewed 76 times ]
Tyfon 75 - 004.JPG [ 427.13 KB | Viewed 86 times ]
Tyfon 200 001.JPG [ 593.85 KB | Viewed 79 times ]
Tyfon 200 016.JPG [ 665.07 KB | Viewed 77 times ]
Zöllner ZM200 & Tyfons 200.JPG [ 568.78 KB | Viewed 78 times ]
Have fun with it.