: Standard extraction and concatenation of the junk files failed to yield a valid binary.
The first file contained the start of the PNG, while the last file ( part2_375.7z ) contained the .
The offset for the hidden PNG data could be calculated by comparing the reported "Packed Size" from the 7z -slt l command with the actual file structure.
The PNG file was striped and hidden in the trailing bytes of the 7z archives, just before the footer.