The second picture with the Kollmorgen scope was especially interesting. According to "cplnorton", Army documents he's reviewd show the Army purchased a few that were of the exact make and style of the "Marine Corps style with audible clicks." Since they were not part of the Marine Corps contract, they do not have MC-XXX markings on the tube. I purchased my example of this variant over 20 years ago.
Happy New Years to all.
Michael