Release Date: July 1977
Released By: Unix Support Group
Source Code: some source code is in the Unix Archive, browsable in the Unix Tree
Documentation: included in the source code

(borrowed from Wikipedia:)
PWB/UNIX (for Programmer's Workbench) was an early version of Unix, started in 1973 by Evan Ivie and Rudd Canaday to support a computer center for a 1000-employee Bell Labs division, which would be the largest Unix site for several years to come. PWB/UNIX was to provide tools for teams of programmers to manage their source code and collaborate on projects with other team members.

PWB/UNIX 1.0, released in July, 1977 was based on 6th Edition Unix. Notable “firsts” in PWB include SCCS, the remote job entry batch-submission system RJE, the PWB shell, written by John R. Mashey, which preceded the Bourne shell, lex and yacc, and utilities like find, cpio, expr, xargs, egrep and fgrep.