Here is a little oddity that I have came across..Not one that would ever be entered into Unitrade, but a nice oddity itself.
Below is a
Scott 014 (O.H.M.S.overprint)...This is what I classify as "
LOW 0"

Notice the placement of the "
0" shown by the GREEN arrow as per the placement of the "
S" shown by the YELLOW arrow...The "0" of the O.H.M.S.is lower that the other letters by
2.61%...Check your own stamps to see if there is a pattern as shown below.

Robert