"Speaking of which, just how common were photocopiers in the National Guard in 1972?"
I can't speak concerning the Guard but I began servicing photocopiers in 1972 and they were in use on Army and Air Force bases at that time. Photocopiers had been in use in businesses for several years prior to 72.
Didn't many of the documents copied by photocopiers of that era start "yellowing" quickly? I worked for the National Archives in the 1980s and recall many documents looking yellowed.