The name plate on my 1212 head says, "SiraTone model EOWS 1212"
I don't know if the 612's or other models go by that name, but in this case I'd say they're the same thing. I don't know what they usually go for, but I paid $200 for mine. The transaction was over eBay, and I picked it up at Pacific Industrial Supply in Seattle.
So my suggestions would be to keep watching eBay (I've also seen a 612 there before) and also try industrial suppliers that deal in equipment removed from various other places.
I'm in the opposite situation that you are. I have the head with the drivers and horns, but need the tone generator and amps! They were in separate places when the siren was installed, as it was on a dam instead of on a pole installation. Pacific Industrial didn't have the control cabinet.
If you do get your hands one one of these sirens, I think you'll be pleasantly surprised at how big it is compared to the pictures.
