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
Why are 1911s and HK USP pistols so popular? - Quora
Hk USP compact 45 vs Hk45c
The Heckler & Koch USP and the Evolution of the H&K .45 Auto Caliber Handguns – Small Arms Defense Journal
Heckler & Koch - HK Poll 50: HK45 Tactical Vs HK45 Compact Tactical. Which 45 would you choose?
Gun Reviews for Astute Purveyors of pew — Hipster Tactical ™
HK45 Heckler & Koch
45 ACP: The Most Powerful Military Pistol Cartridge Ever
Comparing the HK45 to the FNP 45
Range Report: HK45 Tactical - The Shooter's Log
10 Best .45 ACP Pistols (That Aren't 1911s) - Pew Pew Tactical
HK USP COMPACT (HECKLER & KOCH) ALUMINUM MATCH WEIGHT COMPENSATOR – MatchWeight