Probably not a Confederate correspondence - looks like it is post marked Rome NY. Might likely be Scotts #65 Rose, Perf 12. Hard to tell from the scan. #64 is Pink, and it does not look pink.
Appears to be addressed to [someone] at Signal Corps, Richmond VA; however the name does not appear to match anyone on this Civil War (1861-65) Signal Corps roster:
http://www.civilwarsignals.org/brow...13roster.pdf The Union was firmly in control of Richmond VA by May 2, 1865, having taken the town on 3 April 1865 when Gen Lee evacuated to Appomattox, so a letter from NY to Richmond would not be unusual.
Are there any contents to the envelop or makings on the reverse side?