PowerPacker

PowerPacker (also spelled Power Packer or Power-Packer) is a file compression utility and compressed file format for Amiga computers. It was developed by Nico François, and distributed as shareware.

Identification
PowerPacker files apparently begin with ASCII "", followed by a two-digit version number. Known signatures are "" and "".

The reverse-engineered source suggests that password-protected files begin with "".

Software

 * aminet/util/arc → ppunpack*
 * ppcrack
 * Ancient
 * http://aminet.net/package/util/arc/ppunpack10-mos (compiles and runs just fine on modern linux)
 * https://github.com/lab313ru/powerpacker_src (Reverse Engineered source code of packer, ported to Windows.)
 * Packer Algorithm Java Implementation
 * The Unarchiver

Sample files

 * Many, but not all, of the .pp files at http://cd.textfiles.com/amigagames/ag-199501/MultiMedia/Diskmags/ ...
 * PPUnpackWOS.lha → sf.pp
 * https://telparia.com/fileFormatSamples/archive/powerPack/