All, the file
http://www.tuhs.org/Archive/Applications/Early_C_Compilers/last1120c-bits.gz
which is a tap(I) tape image, contains a file called libc.sa, dated Jun 7 1972.
I never noticed until now, but it contains the source code to the C library for
the last1120c compiler. I've added it to the subversion repository under src/lib.
Cheers,
Warren