Alvin,

For all A-D years, the accessory dual horns were seashell horns. The standard single horn from 47-52 was the horn shown above (I think it was called a clarion style horn - maybe someone else knows what its shape was called ).

The standard single horn in 53-55 was the seashell horn. It was mounted on the intake manifold in 1953 and it was mounted on the front of the radiator frame in 54-55.

Dual seashell horns were mounted on the firewall, near the location where the deluxe heater motor came through the firewall. In 54/55, the accessory dual horns were mounted on the front of the radiator frame.