All you needed to undo a shar (shell archive) was a fairly common Bourne shell. We had uuencode to make things 7-bit clean. Some programs to make shar files uuencoded the archived files, but some didn't.

"shar" files existed because "tar" wasn't particularly standardized. As late as 1990, SGI Irix "tar" did bytes in reverse order from SunOS "tar". You had to convert bytes to untar a SunOS archive on Irix.