See the below taken from the Veterans Administration Military Headstone website:
"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 Cong., Chap. 631), authorizing the furnishing of headstones for the graves of Confederates who died, primarily in Union prison camps and were buried in federal cemeteries.
"Congress adopted the same size and material for Confederate headstones as headstones for Civil-Spanish War deceased. The design varied in that the top was pointed instead of rounded and the shield was omitted. Apocryphally, it has been said that the pointed top was adopted to prevent "Yankees" from sitting on Confederate headstones. An act on Feb. 26, 1929 (70th Cong., Chap. 324), authorized the furnishing of this type of stone for graves in private cemeteries, as well.
"On May 26, 1930, the War Department implemented regulations for Confederate headstones that also authorized the inscription of the Confederate Cross of Honor in a small circle on the front face of the stone above the standard inscription of the soldier's name, rank, company and regiment."