Hi, I'm still not exactly sure who made that siren, but it's not a Denver.
http://youtube.com/CrazySirenBoy
Proud owner of: Thunderbolt 1003, Thunderbolt 1000, STH-10A, Model 5BT, Model 5B, Model 3B, Model 2T (noon daily @ 1/2 voltage), Model 2, Decot, Sterling Little Giant
I just assumed it was a Denver because two different people who commented on that video said it was (one person even gave the model number as M1-16H). I'm not at all familiar with the ancient sirens like that.