Thank you for your reply and assistance, Bartamos,

Following your advice; the three wires are colored as described (red/hot, black/horn, green/horn button). With the hot and horn wires connected to the relay, the horn button wire was disconnected, and a jumper wire was connected to the empty terminal on the relay. When the jumper was touched to the negative terminal of the battery, the horn sounded.

As to your other questions:
*The relay was not replaced and appears to be factory original.
*No wires appear to have been changed. I have made no such adjustments.
*I have not removed nor replaced the horn trumpet.
*Steering column appears original, as built.
*No other connections or parts were removed or dismantled below the steering wheel.

Per your message, this result indicates the horn parts being reassembled incorrectly. I am most curious to learn where the problem occurred as the three clutch head screws, plastic spacer, metal “cup” and (for lack of the proper name) flexible contact plate, all went back in the same order and position as removed.

Thank you again for your time and assistance in this matter. I await your further comments.

Jim