If you want a Langstroth brood box that is the same weight as a National brood box...
Depends, any box that has brood in is a brood box...
Tell me, what universally understood generic word for the box that we all know we are talking about would cause you to be happy?
Yes, from a nit-picking point of view, any box with brood in it can be called a "brood box", any box that is above another box can be called a "super", any box that is deeper than any other box can be called a "deep" and likewise the other box in the pair can be called a "shallow", etc, etc. Oh, and any box that is used any particular country can be called "national". But you, I and the original poster all know what we mean when we say "national", without having to search for some other odd word that is nit-pick-proof.
And there are around 90 sub species of Langstroth...
Yes, for example Dave Cushman's site lists a number of those subspecies. For the record, the subspecie that I use for my calculations has a comb area of 0.186 m2 per frame. About four-fifths of the frames listed on Cushman's site have a size that is broadly similar to the size that I have used here.
...and three common national sizes.
I know of only one common National size of the box that I had previously called a "brood box" but which you want me to use another word for to avoid creating the impression among impressionable beekeepers that only that box can be used for brood. Can you tell me of the other two?
But of course neither of us knows what is in a book with that title at this moment.
Fortunately Howland Blackiston also write "Beekeeping for Dummies", which I do have. On page 291 of the 2nd edition he has a plan for the Langstroth hive he uses. The Langstroth in that book has a frame whose height and width is within 3 mm of the height and width of the Langstroth frame that I had used for all my calculations, so I'm quite happy with what I wrote in my previous posts. I hope you don't think it is unreasonable or unrealistic of me to assume that the dimensions of the Langstroth in Blackinston's second book in the series would be the same as the one in the first book in the series.