I did check Pate's book. Also, I have seen a couple of those .25 autos with Parkerized finish and USP markings. Both the finish and the markings were fake, quite obvious to the experienced eyeball.
I don't think I said the military never bought .25 Colts; they certainly did. I said I was highly skeptical of USP markings on them. Pate shows 5 .25 pistols with USP marks. One picture (407667, p. 175) is too dark to analyze. The other four (p. 182-183) are all, IMHO, fakes.
I won't go into detail here, but I have looked at those pictures and, as I said, a couple of other .25 pistols purporting to be USP marked and do not consider any of them genuine. Nor do I believe that any agency/unit put those USP markings on. Guns might have been returned to the factory and marked there, but then the markings should correspond to equivalent factory markings.