Here is the live connection from the power house to the distribution network. It's only a guess on my part, but this might represent the third generation of connectivity as the utility upped their distribution voltage.

As a completely unscientific guess, maybe they went from 2400, to 7200, to 14,400 over the years. The use of two disks in the string says something at or over 15,000 volts. Rough rule of thumb: count the number of disks, subtract one, and multiply that by 15,000, and you're in the ball park.

Dave Dahle replied with a better rule of thumb, which in this case still gives us 14,400 volts for this setup:

Out here, two disks is the standard for anything between 12.5 and 13.8kV.

That rule of thumb breaks when there is only one disk and I have seen lines that used four 6" disks (according to your rule of thumb, it would come out to 45kV vs. actual line voltage of 22kV) and six 6" disks (again, 75kV vs. 34.5kV)

Just sayin'. :)

A better rule would be 7200 volts per 6" disk and 12kV per 10" disk.