M Ted,

If the School he taught at says that he was a professor, he was a professor.

According to merriam-webster is can call himself a professor by three of the four possible definition. He was most certainly using definition 2 b.


http://www.merriam-webster.com/dictionary/professor


pro·fes·sor
Pronunciation:
\prə-ˈfe-sər\
Function:
noun
Date:
14th century
1: one that professes, avows, or declares
2 a: a faculty member of the highest academic rank at an institution of higher education b: a teacher at a university, college, or sometimes secondary school c: one that teaches or professes special knowledge of an art, sport, or occupation requiring skill.

I think that about settles it.