It would make sense that the Marine flag would be based on the 1st National, as that was the naval ensign for a long time after it had passed from usage in the field army.
@ladyoutlaw03 : Best of luck with your new group. One of the things about the c/p/h movement is that they´re very much about right place and right time for unit impressions. So unless you have a location where you can be Confederate Marines all or most of the time, you´re going to hear something like ¨Uh... there were no Marines present during this action so, no, your impression will not be allowed.¨