S&W 625 fully suppressed revolver
The PSDR 3 is a fully suppressed .45 ACP Smith & Wesson Model 625 revolver developed in 1993 by Joe Peters, under contract from Northrhine-Westphalia, for Germany’s SEK (SWAT) teams.
This photo is from Visier Special 6, 1997 (special edition of one of the three big German gun journals)
This gun brought to you by a nation with an apparently compulsive need to over-engineer all things mechanical.
(note: I can't recall what site I found this at, so no credit to the original source is available).