Hi Neil
Welcome to the forums.
In summary, you have the VIN tag 82911CH173724 and the Body Identification Plate with the Model Number 82911M and Body Number 11453-B. The details on these tags are consistent with each other.
A problem arises with identification of the vehicle, in that, with the absence of the ADR compliance tag, there is nothing to tie these two tags to the car to which they are attached.Under normal circumstances there is a cross-check between Chassis Number that is stamped onto the ADR tag, and the Chassis Number that is stamped into the inner guard. These two numbers must be identical. For this reason, and without meaning to cause you alarm, t has been my experience that it is common for ADR tags to "go missing" where a car has been rebodied.
If you provide the Chassis Number that is stamped into the inner wheelhouse/guard - I can at least confirm or deny whether this number appears to agree timewise with the other numbers. This will provide strong (but not conclusive) evidence that the vehicle appears to be genuine. The likelihood of the car being genuine will also be enhanced if the vehicle displays the numerous identifiers of an LC GTR or XU-1.
Cheers
Bazza