Journaling
Dad was promoted temporarily to Tech Sergeant on 1 May 1959. Thirteen months later on the 28th of June 1960 his promotion was made permanent effective 1 June 1959.
“Within air force enlisted ranks, promotion to technical sergeant has historically been the second-most difficult rank to achieve and is the most difficult promotion that most career air force members achieve. A staff sergeant must have served at least 23 months in grade to be considered for promotion to technical sergeant. It normally takes 10–12 total years of service to attain this pay grade. Technical sergeants mentor junior enlisted personnel while preparing themselves for promotion to master sergeant, the entry rank of the senior non-commissioned grades.” ~wikipedia