Well, as best memory serves from long, long ago, the brake had no discernible effect on my K-38 (other than to surrender its finish to the muzzle blast)------seems like the one on my Model 41 worked about the same, so I got a new one for the 38 (just for show), a new one for the Model 41 (also for show), and didn't use the one for the .45. I've heard tell they made some for the K-32, but have never seen one.
So---down to business: I have one for a K-38. It's been used, which is to say the surface facing the muzzle is sans finish (shiny black anodizing) for about half its surface (which is now shiny aluminum colored aluminum). The first PM saying "I want it" or some equally foolish phrase will find it in his mail box----assuming he had the good sense to tell me where the mail box is.
As an aside, it fits nicely on wide rib K-38's of the '50's, and not so nicely on later versions---at least the later versions I have. I've been told it will fit on the later versions if I "spring it some". I have successfully resisted the temptation to try that sort of Bubba-trick----not my style.
Ralph Tremaine