This hinged box comes from my parents/grandparents basement. It is approx 18"x18"x10"h. On the outside is a small brass plate with Japanese writing on it.. There are two small hooks on either side to keep the case closed. Opening the case, you see it has been designed to hold twelve wooden blocks with metal prongs, and the prongs fit into holes drilled into the case. (photo attached) It appears that the boxes have been assembled using screws, and I can only imagine what is inside them. Each block has a small brass plate on it, which shows the block's place in the matrix, and has both Roman alphabet letters and something in Japanese. Blocks in the 4 rows are all labeled A, B, (C is missing) and D. Row A blocks are all labeled "20.0 - 13.0 KKC", row B labeled "13.0 - 8.0 KKC", row C blocks are missing but presumably cover 8.0 - 4.5 KKC, and row D is labeled "4.5 - 2.5 KKC". Blocks in the first two columns (labeled 1 and 2 in Japanese) each have four metal prongs, and blocks in the third column have six prongs, and a japanese symbol which has been loosely translated by a friend as "control".
I believe this to be from the ww2 era, possibly these are some sort of cryptology keys and the ranges correspond to wavelengths; an artifact from the Japanese imperial army according to one friend of a friend.
Would appreciate a knowledgeable opinion.