Usually you can find relatives or neighbors enlisting in the same units, I suspect the Thomas W. Truss, whose records also show enlisting at Ashville on 1 March 1862 by Capt. Lloyd, to be a older brother of Marcus Truss.

Thomas W. Truss's age is noted as 34 at the time of his disability discharge in April/1862.

http://www.findagrave.com/cgi-bin/fg.cgi?page=gr&GSln=Truss&GScnty=83&GRid=20440697&