Bujutsu -- I just went back and downloaded the image of that card, rotating the image 90 degrees counterclockwise so that I could read that red cancel rightside up. It more-or-less confirms for me what I thought before. That strike is, I think, a non-postal one. It looks instead to me like something applied by a company, something either for their internal purposes or something similar. I can't read Japanese well, and this is old Japanese, but I'm pretty sure there's no date on it. Tonymac could probably shed a little more light on it, and it may have informed his post earlier up this thread.
There is always the possibility that I'm wrong, and there are a couple of semi-regular visitors to this board who know a lot more about this than I do, so if you're not in a rush to do something with these cards, you can pursue it a little further. (I believe member "Prahanoaki" is a native Japanese speaker, for instance.)
Another route to trying to extract the maximum possible value of it is to offer it on
ebay with as many relevant keywords as possible, including the name of the company. There is always the possibility that this is an elusive propriety cancel -- you just never know.
Again, I wish this were an area I knew better and on which I could offer a more authoritative opinion to give you more confidence in your valuation.
Keep us updated in anything more about it, in case you learn more about it off-thread,
-- Dave