The following was extracted from a Research Unix V4 distribution obtained from
the PDP-11 Unix Preservation Society (PUPS, see https://minnie.tuhs.org/PUPS/):

.th FILE I 11/1/73
.sh NAME
file \*- determine format of file
.sh SYNOPSIS
.bd file
files
.sh DESCRIPTION
.it File
will examine each of its arguments
and give a guess as to the contents of the file.
It is the only program that will give
device numbers of special files.
.sh BUGS
If the file is not instantly recognized,
its type is given as `unknown'.
There should be some heuristic to
recognize source file `signatures'
in each of the standard languages.