No new changes have been made to the USP platform since 2009...
1993: Original USP9 and .40.
1994: Reduced the slide weight by 1.1 oz.
1994-95: Change to a polygonal rifled barrel (Prior barrels were standard land and groove)
1994-95: Change trigger transfer bar.
1994-95: Change recoil guide rod to a "captured spring version".
1995: Change trigger mechanism.
1995-96: Add rubber spur to hammer.
1995-96: Change angle on slide lock.
2000: Add locking feature to hammer strut support.
2001: Converted captive recoil spring retainer from c-clip to machined end on USP Compacts.
2005: Change firing pin and firing pin block.
The pistol can be dated by the two letter date code on the left side of the slide. This will indicate the year the pistol was proof tested...
A B C D E F G H I K
0 1 2 3 4 5 6 7 8 9
Other markings on the slide include the Stag Antler, which is the symobol of the proof house located in Ulm Germany HK uses to proof test it's pistols. The Eagle is called the "Bundesadler" or "Federal Eagle", a common mark found on German Federal insignia. The "N" which it sits atop stands for "Nitrozellulose", a universal symbol found on German firearms that use modern Nitrocellulose based propellants.
In addition, the pistol can be converted to V9 (safety only, no decocker) or V3 (decocker only, no safety) easily by swapping the detent plate to another respective detent plate. The pistol can also be converted to LEM (a DAO type trigger with short reset) and can also accept a Match trigger kit if you so desire.
As far as buying used I wouldn't worry a bit. HK pistols are very durable. I wouldn't look for anything specific that you otherwise wouldn't normally look for when buying any other brand of used handgun.
"Don't hit at all if it is honorably possible to avoid hitting; but never hit soft." ~ Theodore Roosevelt
Last edited by H&K 4 LIFE; 11-16-2012 at 11:12..