These files were originally to be found in CTAN directory macros/plain/contrib/samples/ While there is little doubt that the author was working at Texas A&M University, there seems to be no actual attribution, and searching the "usual sources" has turned up nothing. The code needs a file date.tex, whose job seems to be no more than to typeset a date. Robin Fairbairns CTAN cataloguer.
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letter1 – Letter formatting macros
A simple set of macros, which acts as a driver file for producing a letter.
Unknown Status, No Information Available|
extensions to Plain TeX for higher-level constructs|
typesetting letters, envelopes, faxes, etc