I noticed that Micro-Trains released a fine looking WP covered hopper this month. I caught WP 11793 at Montgomery, AL on 03/10/1985, just three digits removed from the M-T model.
Found plug door boxcar WP 64728 at Knoxville, TN in the fall of 1977. The car stenciling shows a rebuild month of 07/1977, so it was fresh from shopping when seen. Built 01/1960.
A very strange looking car. The door seems strangely short; it's not often you see the side of the car above the upper door track. Usually that sits right at the eave of the roof, and the door is the same height as the side. I wonder what purpose this serves, maybe the insulation on the roof is thick so the inside height of the car is lower?
I noticed that too. Hoping for an answer, I looked in my 04/1974 Railway Equipment Register and this series of car isn't in there. I'll bet they were renumbered during rebuilding in 1977. However, I did find that WP's 60001-60050 series has nearly the exact same dimensions with plug door and it shows they were for "suitable for coil tinplate", had "Heavy Reinforced Floors" and were Insulated. So, that likely explains it all.
While we're on a WP freight car theme, here's double-door boxcar WP 38159 at Laurens, SC on 08/21/1998.