I'm so old, that in 2nd grade school we still used ink wells, and ink dip pens. (And yes I did get whacked for dipping a girl's pigtail in the well.) But they were replaced by ballpoint pens, But ballpoint pens in the 50s were terrible. They leaked ink profusely. If my memory is right, leaky ballpoints became less frequent in the 60s and still less in the 70s, but were still common enough that engineers had good reason to wear pocket protectors. After the 70s, undamaged but leaky ballpoint pens seemed to disappear. It has been many years since I saw a pocket protector for sale in a clothes store. Clearly there was an advance in engineering that eliminated the leak problem. What was it? Who should we credit?