Found this Sterling M-10 fire siren with one square horn (or intake vent as I understand it actually is) and one round horn at Gainesboro VFD in Gainesboro, Virginia (Google Maps Link). It's actually less than a mile off my work commute, so if anyone wants better pictures I can easily get some later. I basically took this from inside my car while pulled over on the side of the road. The sun was starting to set.
Full size: https://live.staticflickr.com/65535/471 ... 56ed_o.jpg
Full size: https://live.staticflickr.com/65535/409 ... 729b_o.jpg
Full size: https://live.staticflickr.com/65535/471 ... c2a2_o.jpg