Thank you M1, a very useful link.
I'm going out on a limb and wondering if Nancy's doc about her dad could mean:
Above 4 Enlisted Men (for) Detached Service (with the) Range Safety Officer ?????
This was a time of intense training for D-Day and range firing would have been carried out.
Colin.
EM from DS with RSO 359th Regt + dy
Okay there's the line. I had to see it again to remember it.
Could be?!
I decided to send the question to several of my historian friends (Fort Leonard Wood, Army Corps of Engineers Office of History, etc.). Let's go right to the top! I'll let you know what I discover.
Here's one answer from Michael Brodhead:
Classification: UNCLASSIFIED
Caveats: NONE
Hi, Marion--
The best I can come up with, and it's only a guess, is "communications
section."
Received a letter from Dave too, and he is looking into it...
Boy oh boy, would I like to just get a hold of morning reports ! they have to be filed SOMEWHERE??? RIGHT??? The only thing the military is good at loosing is our IDs and medical reports!
Got the answer regarding what "cs" stands for in morning reports. Many thanks to Professor Dave Ulbrich and Dr. Larry Roberts. 
No we no longer have to go by hearsay.
Classification: UNCLASSIFIED
Caveats: NONE
Marion,
Dr. Roberts tracked it down. He is amazing!
The abbreviation "cs" stands for "current series" and refers to the current
series of orders, pubs, regulations... What ever form was current at the
time, as opposed to an obsolete form or different/unique format. It is a
records management citation.
Dave