The older Kahrs are very nice, robust and reliable pistols. The original nickel plated ones are somewhat rare and IMHO desirable.
The standard trigger on all early K9s was the longer pull, later came be called the NYPD after a number of trade-in K9s hit the market. The shorter pull trigger was introduced in the 1998 Elite model and hence that trigger became known as the "elite trigger". At that time the standard K9 trigger remained the longer pull. I don't recall the year precisely but around 2013 or so Kahr switched the triggers so that the "elite" trigger became the standard and the longer pull was separately labeled on the box "NYPD".
Differences between an old K9 and a modern K9 include a altered trigger bar and different dove tail cuts in the slide. The Kahr website explains the sight dove tail differences. Grip panels should fit from either era. The early frames were flat above the trigger guard and later model sport a sculpted cut along the top of the slide. A visual not mechanical change. There are probably other design changes but I can't recall others.
Judging by today's left wing, looks like Senator Joe McCarthy was right after all.