I do realize that. But look at any importer like CVA or Navy Arms, some guns aren't even marked yet we can sometimes surmise the original manufacturers for parts, or by comparing parts and features.
But even if PR is determined, where the parts came from may still not be known.
There are lots of anonymously made products in the world, and even when the manufacturer is known, the names of the designers, subcontractors or the actual workers aren't.
What we don't know about or care to know doesn't bother us, but a couple of unknown initials stamped on a product do seem to.
I can understand the desire to know, but then there are so many other products built with similar anonymity that it shouldn't be too much of a disappointment.
If someone said that they had a gun built by Pierino Ruschetta, who else would recognize it? If you said that you have a PR, then more folks would. The maker chose to use the initials and not his name. If he had become famous enough for it to matter, then his name would be associated enough with his initials to be known far and wide. But in this case they are not, so the actual name of the builder may not matter as much for identification as the 2 simple initials do. For instance, it doesn't seem to be a matter of great enough importance that it would affect the gun's value at all.