Truck/Emergency Air Horns

[The Foos]

I'm taking a stab in the dark here and hoping someone knows a thing or two about truck/emergency air horns.  My question is who is the manufacturer of the air horn used in the video(go to 2:30 to hear the horn).  I think it sounds like a Grover 1510 stutter tone air horn but I'm not 100% sure because other sound clips I've heard of the 1510 don't sound quite the same (slightly higher pitch).  If anyone could provide any opinions/input it would be greatly appreciated.  Thanks.

http://www.youtube.com/watch?v=hpDnFH4pPf0

[ALCOHolic]

Sounds like a Grover 1510 Stuttertone to me.