This is what I got off of ancestry.com:
branch: immaterial-warrant officers usa grade: private
Warrant officers, before 1989, were not commissioned by the president. In stead, they held warrants that were signed by the Secretary of the Army. The grade of private is that of an enlisted man, and I do not know how that could be tied to warrant officership, though he could have been a prior enlisted man. WO's are technical experts at their jobs, and are usually E-5's before they train to become one. The stand below O-1 officers, but above academy cadets and all enlisted men. They are treated as officers (salutes, etc.). Hope this helped, and take a look at the Wikipedia page for Warrant Officer.
try to find out what unit he was with.