According to the NASA Satellite Situation Report, Apollo 5 was launched on January 22, 1968 as 1968-007, i.e., the 7th launch of the year 1968. After separation, the ascent stage was given the designation 1968-007A. It re-entered on January 23, 1968. The descent stage was designated 1968-007B. It re-entered on February 12, 1968.
The S-IVB stage that launched them was 1968-007C. It re-entered on January 23, 1968.