First we tested the 16 with the 100 grit block. The space between were about 2 years apart, each time. Sometimes it would move every 3 or 4 years. Are test takes place between 78 years. To get to its final place it took a very long time.
Second, we tested the 19 with the 100 grit. The space between movements were about 4 to 7 years. This longest time between movements were about 9 years. The test took place between 78 years. To get to the place it is today.
Finally,