I have a N. miranda and after a vigorous search I found out it is: N. maxima x. N. x superba. 'Miranda' has been around since before 1960 and the leaves all seem to grow 2.5 feet in lenght and 8 inches to a foot wide. It can grow as a highland or intermediate. My sources are
Gordon Cheers A guide to Carnivorous plants of the World P. 13
F.A. Novak The pictorial Enclopedia of Plants and Flowers P.105
My plant and a ruler + various internet sites.