This siren looks like a B&M Siro-Drift Model S8B, S8 being the model number, and B standing for the brake (the large coil on the back). It also looks like somebody removed the finger guards in the slots, where there are little holes, 4 per slot. These sirens are known for having a very rich, old-school tone to them. One can also send them to B&M Sirens to have them restored professionally! I'd jump on this, I think it will clean up very nicely.