Short Answer
It depends….This one stumped me at first….My battle buddy and SME SGM(R) Linda Kessinger pulled me out of the fire with her expertise.
Discussion
According to AR 25-50 the senior individual goes on the right. When in doubt as to the seniority, use the signature of the official whose organization is the same as the letterhead. Simple RIGHT? Not so fast!
Now for TWIST #1:
For this we go to AR 600-20. Let’s say the individual’s are of the same rank and are in the same unit. What would you do? Here is what we came up with. The individual with the earlier date of rank is senior so they would go on the right side of the document.
TWIST #2:
Unless of course one of the individual is in senior in position. For example you have 2 Sergeants (E-5). One is a Squad Leader and the other is a Team Leader (TM) and the the TM has an earlier date of rank. The Squad Leader would be placed on the right because they hold a senior position. .
Reference
Extract of AR 25-50
Section II, Chapter 2-6 (b5) page 30 reads: