This horn is so loud I am tempted to put it on my motorcycle and blow cars out of my way!  It is an Italian made Stebel compressor and pair of air horns, originally sold by Montgomery Wards as a "Riverside Wayfarer" component, their model 61-7791.  Itis 12VDC.  I hooked it up to a spare battery, the compressor comes on, and the horns put out LOTS of noise!  I checked both horns individually and they are both fine. One  horn is missing a screw and washer, I have no idea of their function.   I don't know the frequency of the horns, one is 5" long, the other is 7" long, not including the diaphragm housings.  This would be great for  your vintage Fiat, Alpha,  or other Italian sports car.  I guarantee to ship the item described, as shown, but due to age nothing beyond that.  Email me with questions or for other view photos.     Ships anywhere in the U.S., priority, for $15.00, including insurance against shipping loss.   In addition to paypal I accept personal and business checks.   International  shipments OK; ask for a quote.  Please wait for my confirming email prior to payment.  No Reserve.