While doing some internet research we ran across some published information about the locations of these marks

1) "GEODESY - DESCRIPTIONS OF TRIANGULATION STATIONS IN GEORGIA" is a booklet produced in 1917 by the Government Printing Office. The information/description of the benchmark located on Kennesaw Mountain:
 

"Kenesaw (Cobb County, Ga., F. P. Webber, 1873). About 3 miles north-west of Marietta on the highest part of Kenesaw Mountain. The station is marked by a cross and the letters U. S. C. S. in the top of a granite post 5 inches square, which projects about 2 inches above the ground. The underground mark is a cross in a copper bolt set in a drill hole in the bedrock about 2 feet below the ground. Three reference marks, each consisting of a copper bolt set in a drill hole in a rock, are at the following distances from the station: 2.01 meters (6.6 feet) east, 3.47 meters (11.4 feet) west, and 3.41 meters (11.2 feet) northwest."

We were able to download this entire document from www.archive.org. CLICK HERE to see the full text.

The current summit benchmark and reference marks in the above pictures do not fit the description of what is found in this text. See the data sheet below for a current description.

2) NGS Datasheet from National Oceanic and Atmospheric Administration. CLICK HERE to see the full report.