1944 Remington Rand question

Someone offered me a Remington Rand serial # 1605xxx (1944). The gun has all the correct markings and finish. The only thing I doubt is the markings on the barrel: it has a small “P” and a “H” on top of the chamber, at the bottom there is a “5” (in front of the ring) stamped. The main spring housing has also a kind of “chrome layer” that what comes off. Can anyone explain these questions?
Thanks

The barrel is from a Model 1911 Colt. Have no idea on the mainspring housing without a photo.

After WW2, USGI .45's had little collectability, & it was not uncommon for folks to take them to a bumper plating shop (car bumpers used to be chrome plated) & have them tarted up. Peeling chrome plate indicates that's where the MSH came from.

Neal