They were for me to be made from late 2006 to early 2007
Found this on the wayback machine
To find it:
go to wayback machine
Type in federalsignal.com
Go to 2006
Scroll down until you see december and the day 6.
Go to the and click on safety pruducts group. Scroll down and find what it says federal warning systems and click on the top of it. At the bottom left it will say. "Federal Announces the NEW 2001-130 - the first 130dB 48VDC Siren in the World.Learn about it here" Click on learn it about it here. There you go. *Unless you are know wayback machine then it wont be a problem.*