Car didn't sell

Well what we now know for sure is that I t was built in August 1990, and I'm guessing it wasn't built in a day. So pinning a build day might be tricky.
But let me do some more fishing.

I was going to add it to my letter to dvla to strengthen my case.

As said by mrb it's a registration date we need

What case, that buyer may never come back, if he's not happy with this evidence sell it to the next buyer.

I've sent him a picture of the form

It H reg 1990 so a date late october to early december would be good.
22/11/1990 was a nice thursday for car registration in japan lol

It deffo 1990 but some DVLA staff input date wrong in first registration section, they done it same as first registration in UK .