How Chief Rabbi Yaakov S. Kassin wrote a Pasul Sefer Torah

As a young man, Yaakov Kassin who would later become the first Chief Rabbi of the Syrian community of New York, was a brilliant scholar and orator. His Bar Mitzvah speech is a genuine work of art. His Father immediately after his Bar Mitzvah, apprenticed him at a local Sofer, to learn the trade of writing Stam. Within months, he finished writing a Sefer Torah which was given to the Yeshivat Hamekubalim Beth El in Jerusalem. The writing was said to be a beauty to behold. Shortly after, his father discovered his birth certificate in which it was found out that they miscalculated his age. He was just 12 years old and not 13, thus the Sefer Torah he wrote was Pasul. (Princely Wisdom, pg 31)
The Sefer is still around and I have been told by people who saw it, that it's beauty is still apparent.