Defunkd

[fabrixnet]

Hi,
I would appreciate some help identifying and valuing this vintage Japan T-shirt.
I personally purchased this T-shirt in London in the early 1980s and have owned it ever since. It has remained in my personal collection for more than 40 years.
The original neck tag reads Sportswear – Size XL – Made in Britain.
It is a black T-shirt with a large red, white and black Japan graphic on the front and a plain black back.
Measurements taken flat:
Pit to pit: approx. 55 cm / 21.7 in
Length: approx. 81 cm / 31.9 in
The shirt is in excellent vintage condition considering its age. I have carefully checked it and there are no holes or open seams. The print is also very well preserved, with strong colours.
I have been unable to find another example with exactly the same graphic.
Does anyone recognize this particular Japan design or know approximately when it was produced?
I would also be interested in any information about the Sportswear / Made in Britain tag and, if possible, an approximate current market value.
Thank you very much for any information.