I belave its a Nathan K5 http://www.youtube.com/watch?v=R60vyJajEjg&feature=autoplay&list=HL1351448481&playnext=5
I cant wait to get em mounted up when ever i get a truck 
They didn’t sound quite right, but that might have been depending on how much pressure you used or the recording on your phone. Have you checked the diaphragms? Make sure you’re getting a good seal. Disconnect the hose and just try blowing through them by mouth. If you can push air through them with your lungs then you should take them apart and service them.
Now that’s thinking ahead!
Whenever I’ve bought a vehicle, I’ve always had an eye out for what I could do with the stereo. My future vehicles will be trainhorn friendly also. LOL
Just the way the camera made it sound. I’m selling my truck and hopefully getting another one. Or if I keep my truck the horns will go on that. Yes almost everything I look at I look to see how much room it has for audio stuff.