NCB I beam (H rotat 90deg) dimensions table

Hi,
V5

I am calling this an I beam (I is a serif I) though it could be a H beam on its side !
I am told its NCB being 80 yrs old.
I draw it as per measurements given, upper and lower parts will get a bit thicker towards middle, BUT NOT THIS AMOUNT. that 4.779 cannot be right.

I cant find an NCB chart anywhere.

Where can I look at the theory of a 4.5 x 6 inch I beam NCB ?

Steve