Really rare books even in Japan. They feature large format and often pull out highly detailed style guides for various trains.
You get three editions. They all show reading wear and creasing. Additionally:
1948 - This book has a fully taped spine (the staple is still present and this was likely so it could be used and read without eventually tearing out pages) and a large piece of the back cover (blank) torn away.
1949 - The cover is separated from the book and the spine was fully taped at one point.
1950 - Has hard cover covers. The original spine tape is in great shape with only a small pull at the back. Definitely the best of the lot.
Overall these books make a good condition set and the few times they are found they are normally all but destroyed. When found these lesser copies sell in the $60-75 range each.