I have no experience with the 639, but I did have a couple of their mags that I used in a Colt National Match .38 special wadcutter and they worked fine.
My experience with Triple K mags for several pistols is: poor customer service, when you attempt to get mags replaced that do not work or the wrong ones were shipped. The quality is generally inferior to factory mags and I will shy away from them in the future. I had floorplates break (plastic) or come off (soldered) and followers all are generally of poor quality.
Triple K Mags for 639
Linear Mode
