Which Tuff wheel is this?!?

That appears to be a rimblow wheel. The horn "button" is the complete inside circumference of the steering wheel. As designed, you just squeeze the rim of the wheel anywhere to blow the horn. They were known for malfunctioning including not working or working when they wanted to and you did not. If you look inside the steering wheel cover, there should be a slot all the way around the inside of the rim of the wheel.