“covered in C-7 incandescent lights from 1963”
Was the light string a series string. One light goes out and you had to replace the first bolb, move it to the second slot, then move that one to the third slot untill you found the burned out bolb.
Nope, they run independently.
In 1974 Dad replaced some burnt out ones with flashers. Each one contains it’s own flasher, so they run independently.
When it’s quiet you can hear them tinkling. Out of 8 originally bought (they came in 4 packs) 6 are running today.