Thanks for the reply.
I am sure I have a 6-volt bulb, but I am not sure it is 5-watts. It's the bulb that came with the Puch to me, but it was never working. I think I know what you are implying, that the bulb could be so high a wattage that the coil can't feed it enough power.
I have a bench top power supply, so I suppose I could feed the bulb 5-volts DC and look at the ammeter to determine the wattage of the bulb.
I will check the continuity of the coil. Is the other side of the coil grounded?
If the coil is bad I will order another, although I still think I could steel 5-watts of power from the horn circuit since it's fairly unused.
If the coil is good I will order the correct wattage bulb (if my bench top supply indicates the one I have is higher wattage) and see if that lights up.
You've given me some things to try. Thanks for that.