I have two guns that are described as so, but not R9s.
One is a hard chromed race gun for IPSC used hard years ago.
It shows no wear what so ever. And talk about potential holster wear! There were thousands of draws! However, the internals are not HC. The external is easily cleaned. The internals are cleaned like anything else, but worse, due to the number of rounds and hard use.
Two other guns are carry guns; an NP3 HK P7 M8, and a custom 1911 Scott McDougal and Associates Officers model with NP3 lower and internals and Rogaurd upper.
These clean up easier than my all my other guns for sure.
After three years of daily carry for the 1911, no signs of leather holster wear.
The HK is carried little. I just "feel" a lot more comfortable in my shoes with a 45. I know KJ understands.
Hope this helps