Not really a typo, a newbie mistake. I've spent several hours reading and attempting to learn as much as possible in the past week or so. All of it essentially a foreign language. Like so many things in the collector world, there is a lot of misinformation and outright mistakes. I've been involved in many different hobbies and learned long ago, when starting something new I don't know what I don't know yet. I greatly appreciate everyone's input. As an example of something confusing to a rookie. Yasugi steel ,,,,,, After reading that post last night I spent an hour looking for details and discovered conversations about Yasuki steel. All I know for certain is Yasugi is a city and may or may not be the trade name of a type of steel made there.
It looks like ALL the small parts and the wood part of the Tsuka (handle) also have a 9 stamp. Yes you are seeing thin gauge sheet metal between the ray skin and the wood. I have not found anything specifically stating what the number stamps indicate.