In late 2014 early 2015 HK introduced the USP9 Tactical. The threaded barrel 9mm USP before then is the USP9SD.
The Tactical has Tactical on the slide, an O-ring barrel, & semi match trigger components. You will have to change a few springs out & the hammer to make it a true match trigger system. Still an excellent trigger though.
The SD just has USP on the slide. None O-ring barrel, & standard trigger components. It’s basically a standard USP with a threaded barrel. Still an awesome pistol.