Frederick, I have just heard back from the VA. This is what they had to say:
"Since we offer different headstone and marker types (bronze, granite, and marble), there are several contractors currently manufacturing them. In the past, contracts were issued annually so there are potentially hundreds of contracts for the headstones and markers. There was little consistency between the contracts in the early 1900s. That is why we have headstones with arches, headstones that are rectangle (flat top), with some that are 2 ½” thick while others are 4” thick, with different fonts, etc." (I know there are at least 3 companies currently making the stones)
"The question of permanently marking graves of Confederate deceased in national cemeteries and Confederate burial plots resulted in the Act of March 9, 1906 (P.L. 38, 59th Congress, Chap. 631-34 Stat. 56). This act authorized the furnishing of headstones for Confederate veterans who died in Federal prisons and military hospitals in the North and were buried near their places of confinement. The design for these grave markers was to be the same size and material as headstones for Union soldiers, except the top was pointed instead of rounded, and the shield was omitted. The pointed top may have been taken from the design of the headstones provided by Confederate heritage groups but the exact origin has not been documented at this time. An Act of February 26, 1929 (70th Congress, Chap. 324-45 Stat. 1307), authorized the furnishing of this type of stone for graves in private cemeteries.
All headstones applications through 1985 are at the National Archives and Records Administration, College Park."
For specific information or to request copies of headstone applications, please write to:

Modern Military
Attn: Military Headstone Applications
8601 Adelphi Road, College Park, MD 20740

And also: "On May 26, 1930, a modified design for Confederate veteran headstones was approved by Assistant Secretary of War P. Trubee Davis. It consisted of a slab design of white marble, 39 inches long, 12 inches wide, and 4 inches thick, pointed at the top, and inscribed with the name of the soldier, rank, company, regiment, with the Confederate Cross of Honor cut within a small circle on the front face of the stone above the inscription. The circle was eliminated from the design around 1987 and the laurel wreath became less detailed and more abstract at this time."
This possibly will keep us from putting a date (with in a time usable time period) on when the stone was ordered and set. Also the statement about the date the cirlce was eliminated is not completely accurate. William Thomas Overby was hung by the Federals in Va., in the 1990's his remains were brought back to Newnan, and placed in the Confederate section of the cemetery. (I cannot remember the exact date, but I am sure someone on this board will know) I just looked at his head stone a couple of weeks ago, we know it was manufactured and set after 1987, yet it has the Confederate Cross of Honor inside a circle. This could have been a request, but still anyone looking at it and trying to use a time frame as to when it was set,( using the 1987 date that the circle was eliminated), would be incorrect. I am currently trying to find out if the government stopped its quality control inspections. I have found stones ranging from the 12" wide standard to 13 1/8" with several in the 12 3/4" range, and still more that were out of spec for the original specifications.
Also as to Mary Mooty's head stone, this is what they had to say:
"At no time were wives of Confederate veterans eligible for government-issued headstones so we have to assume that the headstones shown in the photographs that you provided were ordered and paid for privately."
I am still looking at all of this, but I believe trying to put any kind of dates on stones will be impossible. Considering that during the last 100 years there have been so many different contracts, and the tools that were used then are no longer in use, and the fact there had to be hundreds of different craftsmen doing the work. Each person engraving a stone had their own little trademark, the lettering may be a little different, the width of a tool, or the kind of tool might have varied from person to person, and whether the craftsman was really dedicated to his work or just wanted to get the job done and go home. Also the different ways of cutting a slab to become a stone has changed several times. I am checking with several SCV and UDC folks hoping they have some records of when they ordered certain stones, and then going to check them out as to measurements, fonts, types of cuts, etc. I am not giving up, but it looks like it will be a long struggle, especially since most SCV camps did not see any need in keeping records of orders or dates they set stones. I will keep everyone posted as I get new information.