When you sent me a private email, I saw no references to Mississippi, just Virginia. It appears this man is the "G. B. Jackson" listed as a member of the 7th Mississippi Cavalry Regiment (CS), aka, 1st Mississippi Partisan Rangers.
Here is a history of this unit:
http://mississippiscv.org/MS_Units/1st_Regt_MS_Partisan_Rangers.htm
Please copy your posting to the Mississippi in the Civil War Message Board at http://history-sites.com/cgi-bin/bbs53x/mscwmb/webbbs_config.pl .
Jim Martin