I looked up the US Code (39, etc.). Forget the other one as it is not a proper legal citation.

39 USC, Section 500 deals with the character, make up and authority of the Postal Rate Commission. It is only a few short sections contained within it, but nothing that I found has anything to do with something like free franking privileges, which is what I thought I was going to find somewhere in the section.

As for the United Nations, and the postage paid indicia, I could speculate that this is referring to the process whereby items mailed from the UN (New York) were handed over to the USPS for handling and delivery.

Now why on a first day cover, it has the indicia instead of the stamp could be because the stamp was from the US. One would have to use UN postage to mail it from the UN. It is usually permissible to put the US stamp near the UN stamp, but maybe in 1960 it wasn't allowed.

Again, this contained much speculation on my part, except for the 39 USC section that I read.

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That's not a very "local post" to deliver something 3,000 miles! Interesting though.

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