I am looking for the "usual" two-letters-hyphen-one-digit type denomination.
This car is shown/mentioned on a small handful of websites including Teikoku's own website, a website about electric Japanese cars of the period and Teikoku's German site, but none of them show any such denomination.
I have a very comprehensive book about Japanese cars of this period and it makes no mention of such a denomination in this particular car's history, so I can't imagine where you have got it from.
I can't find it so I'll have to leave it for someone else. Thanks so far.