Yep, and very typical of how things were/have been here for a long time. There is no VIN on the windscreen or anywhere else. The chassis number and other codes does the same job but in a walled garden. Even the colour codes are different and opaque. Someone once memorably described the entire economic/regulatory system here as protectionism on steroids. It is deliberate because it makes it difficult for outsiders to sell in the Japanese market and also more difficult for non approved traders to buy in the Japanese market and export to other markets.
I got a reply from my contact at Honda. He is seeing what manufacturing information he can get hold of. Even though he is pretty senior he is not in a department that routinely needs this information so he will have to ask a favour to get it. Another problem is that more generally, information is regarded as valuable and is almost always confidential and heavily protected.
