Gene,
I just went a double checked and they are 681 & 682. The domed cover has the dime size hole with the red plastic insulator where the wire connects. The mounting bracket is a piece of flat bar stock about 4" long that has about a 30* kick in it close to the horn and two bolt holes. If you put the horn bell flat on the table one horn has the bracket riveted at 8-o'clock and the other is at 4-o'clock. The brackets go straight away from the horn like a lolly-pop stick except for the kick.
The horn (less bracket) looks like the ones on my 1956 trucks, but they are stamped "12V", so I'm assuming these are 6v.
Hope this discription doesn't confuse things...
Thanks,
Mike B