:: I have a MIL-SPEC part number, MIL-C-9084-C, but the description I have is:
: "Fiberglass, A-finish class 1 and 2 type 3, satin nbr 120, 38 in
: wide". What does this mean? Is this 6oz or 4oz? Can anyone look this
: part number up somewhere and help me out???

According to the information on George Robert's and FiberGlast's web sites, type 120 is 3.2 oz. Satin E glass, which is what George uses (in multiple layers) on his own boats. Two layers of this will give you a stronger boat than a single layer of 6 oz. glass.