According to the N&W's pamphlet "Coal Car Equipment" (an interesting 1992 Heimburger reprint of an original dated 1944--I strongly recommend you try to get this book, and good news: it appears to still be available from Heimburger!
Anyway, the 50 ton Class H5 was in the series 84000 to 85999. The photo shows number 84355. I cannot find a built date on the photo in the booklet. According to the booklet in 1944 there were still approximately 9745 of these cars in service. A footnote indicates that the cars would be renumbered during heavy repairs in the summer of 1944.
The other 50 ton hopper in the booklet is Class H1 which has side panels that extend below the side sill with tiny dump doors at the bottom and is a very distinctive looking car. For what it is worth it is series 33000 to 37999; 71000 to 72499, 74000 to 77267. The built date appears to be 5 -10 and the rebuilt date 7-25.
The HL class you mentioned is listed as a 55 ton car and the built date in the photo appears to be 6-36 although it might also be 6-30. Sorry the geezer has a problem with fuzzy photos! I found a reference to a drawing in RMC of this car which refers to 50 tons so there seems to be some confusion on that point. I guess I trust the N&W's own book which after all was probably meant for customers, not railfans, and accurate tonnage was what the customer surely wanted to know!
The booklet has photos and crude but usable drawings with basic dimensional data. You mentioned the peaked ends. They give the capacity "level full" but also "heaped." Interesting! Also interesting are the many gondolas they list as coal carrying, not only low side types with drop doors but those huge 90 ton battleship gons with 6 wheel trucks of a unique style and solid floors.
The April 1969 Model Railroader had drawings of the USRA/ARA 55 ton hopper. It does not list N&W as an owner.
I hope this helps.
Dave Nelson
