Apologies in advance if this is not the best place for this question. Apologies also that I couldn't "tag" this question very well as I had to fight with the tagging system for 5 minutes before I could post this question with a tag that was not completely irrelevant :( If anyone is familiar with currency/banknote tracking, e.g. Where's George or EuroBillTracker, I am currently working to build one, I'm working on one of my own, for the Japanese Yen. Eventually I will make a "generic" version and post that free on GitHub so that anyone with PHP knowledge can make one for their own country/currency (instead of it being like currency tracking where every tracker organisation has to write their own tracker project code from scratch), but that's a long way off yet.
My question is about a symbol I've seen in some images of Yen banknotes, with particular reference to the serial number (which is key for bill tracking). If you look at this image from Wikipedia (although there are other examples of notes with the same character) here: https://en.wikipedia.org/wiki/Banknotes_of_the_Japanese_yen#/media/File:1000_yen_Natsume_Soseki.jpg
You see that the serial number of that bill is: ZP5494(something)4U
Where I wrote (something) in there, it is because I cannot understand what that symbol is. As I understand it, the currency nominally has the Roman alphabet and Indo-Arabic numerals, like Western currency, but this symbol looks to me to be an exception of some kind. It looks like a cross between a 2 and 9, or a 9 with a tail on its bottom, or something, but I have no idea what that is. Does anyone know what that might be or where I can find out?
Thanks in advance,