Can you explain what these small holes are? They appear to be the letters "UN" but are upside down to the orientation of the stamp. I have several that appeared on the same cover. (No longer have the cover but it was quite likely sent overseas.) As you can see, the stamp appears to be Scott #720.
Answer Hi Joshua,
It is a perf-in, which is an abbreviation used in the hobby for "Perforated Initials". They were used by businesses as an anti-theft device. If an employee would steal the perfin stamps and use them privately, they would be in big trouble! This is a popular collecting area, and there is a special catalog that lists and prices them (which I do not own). Nor do I know the name of the company that used "UN". The fact that they are inverted is not real unusual and generally adds no premium. Hope this helps.