By Naval Jack I assume you mean the blue field with 13 stars, but no stripes, correct? What is the arrangement of the stars?

I have never seen a 13 star "Naval Jack" but your flag could be a copy of George Washington's positional flag as Commander in Chief. See http://www.fotw.net/flags/us-washi.html

The zig zag stitching of the stars tell us the flag was made after 1895.