Not a Grifco 777, for sure.
If that is a siren, the closest thing I can think of is a Skil Alarm Master from Australia, which is HIGHLY UNLIKELY as they barely made it out of the state of Victoria, only about 3 exist in other states in Australia, so I doubt any made it overseas.
Even a Skil Alarm Master looks a bit different to that, I don't think it's a siren.