There are many old telegraph poles still in use in my town. They are the pre-notched type of pole. Pre-notched, in case more crossarms had to be added at a later date. All of these poles in my town have a total of 6 notches per pole. What I was wondering is, what year did they stop pre-notching poles ? Knowing this, will help me narrow down the age of these old poles. If you look at my photo closely, you can see the notches. Thank you for your help.