The storage, use or other consumption in this State of property purchased from any unincorporated agency or instrumentality of the United States, except (a) any property reported to the Surplus Property Board of the United States, or to any agency succeeding to the functions of that board, as surplus property by any owning agency and (b) any property included in any contractor inventory, is exempted from the use tax.

“Surplus property,” “owning agency,” and “contractor inventory” as used in this section have the meanings ascribed to them in that act of the Congress of the United States

known as the “Surplus Property Act of 1944.”