These are two great handguns manufactured by the premier company Heckler & Koch. In 1995, they developed the HK USP Compact, the with a few modifications they brought the 45C to market in 2007.
Hk USP compact 45 vs Hk45c
Gun Review: HK USP Tactical .45 - The Truth About Guns
10 Best .45 ACP Pistols (That Aren't 1911s) - Pew Pew Tactical
A Battle of HK .45s: HK USP Compact vs HK 45C
Guns.com: Weekly Gun News Featuring: Taking a Look at the FN 509 LS Edge
The Heckler & Koch USP and the Evolution of the H&K .45 Auto Caliber Handguns – Small Arms Defense Journal
MK23 Suppressed Pistol: Why the Navy SEALs Love this Gun
an actual gun thread in GD!!! HK USP .45 range report
HK45 Heckler & Koch
Why are 1911s and HK USP pistols so popular? - Quora
FNP-45 Tactical vs HK 45 - which would you pick? [Archive] - Forums