Autographing a stamp not only establishes you as the postmaster of the contract but constitutes a cross-claim. Using the stamp process on documents presents your adversaries with a problem because their jurisdiction is subordinate to that of the UPU, which you have now invoked for your benefit. The result in practice of doing this is that whenever those who know what you are doing are recipients of your documents with autographed stamps they back off. If they do not, take the matter to the US Postmaster to deal with. If he will not provide you with your remedy, take the matter to the UPU for them to clean up.
Use of a notary combined with the postage stamp (and sometime Embassy stamps) gives you a priority mechanism. Everything is commerce, and all commerce is contract. The master of the contract is the post office, and the UPU is the supreme overlord of the commerce, banking, and postal systems of the world. Use of these stamps in this manner gets the attention of those in the system to whom you provide your paperwork. It makes you the master of that post office. Use of the stamp is especially important when dealing with the major players, such as the FBI, CIA, Secret Service, Treasury, etc. They understand the significance of what you are doing. Many times they hand documents back to someone using this approach and say, "Have a good day, sir." They don't want any untoward repercussions coming back on them.