If I am not mistaken, this man belonged to Capt. Tanner's "Jackson Guards". As Dale Cox noted in a recent post, the greater part of these men deserted before being assigned to a Confederate regiment (11th Florida Regt.).

http://history-sites.com/cgi-bin/bbs53x/flcwmb/webbbs_config.pl?read=2323

We can see that significant numbers of men from West Florida who deserted from Confederate units later joined U.S. commands. Many of those later deserted U.S. service as well. I guess it got to be a habit.