A very special type of polysquare puzzles is the set of 'square-puzzles', where all given shapes are squares with integral sidelength.
Reference
... Bezopastnosti[?] (NKVD, 1934-1943) Ministerstvo Gosudarstvennoi Bezopastnosti[?] (MGB, 1946-1954) Komitet Gosudarstvennoi Bezopasnosti (KGB; ...