SQX
From Just Solve the File Format Problem
SQX is an open-source archiver developed by Sven Ritter and SpeedProject.
The source code download includes a text file giving file format details. The source code is archived as a .sqx file itself, but fortunately an SQX extractor is also included as a standalone Windows .exe. (Bad luck for users of any non-Windows platform, though.)
The terms Squeez and UnSqueez are used for some of the software and technology associated with SQX format.
Identification
ASCII "-sqx-
" appears at offset 7. Though this is reminiscent of LHA compression identifiers, SQX is not closely related to LHA.