I have an old cast iron cover &amp; would like to learn more about it &amp; the year/model of tractor it goes on.  It is a set of wings that are marked Hart Parr on a base.  I believe this is a radiator cap?

Part No's - 13028 (Top Wings)
                13027 (Base that wings are attached to)

Any help would be greatly appreciated.  I collect old UNIQUE cast iron peices &amp; ran across this little treasure!

Thanks Alot! ~MARY~