My US NSX serial number is MT000085. I am fairly certain that the mfg date is 6/90. I can't look right now, but I remember Gary M asking me that question when I first got it in 2000.
The way the story goes is that the first 63 serial numbers (01-63) were pre-production cars and thus the very first (US, at least) car was number 000064...+/-. This would make my car the 22nd production car in the US. When removing my door panel, it had "#22" hand-written on it with a marker. This may be normal for many or all cars or just a coincidence. The other door had #23, so go figure (mixed up?).
Having said all that, I feel it is extremely unlikly that any US (or Canada) model would have a mfg date earlier than maybe 5/90 and probably 6/90 is the earliest because they were really banging them out right then.
My car was originally delivered to Apple Tree Acura in Ashville, NC and purchased in very early September of 90.
Several years ago, I noticed #79 for sale and called out of curiosity (the guy was in Tennessee, but the car was in Florida). I never laid eyes on it, but it sounded ligitimate. Besides mine, that was the only production car I've ever heard of that was even below 100.
Also of interest possibly: I think the shell in front of the factory is actually #000001. One of the cars featured in the black and silver brochure is #000004. When speaking to the guys at RealTime Racing, they said their NSX race car was #000003 and that they also had #000009. All of these would of course be preproduction cars. It is rumored that most of the preproduction cars were destroyed/recycled/crushed.
I'm sure that some of the other 20 cars earlier than mine besides #79 are still out there. I've just never heard of them.
HTH,
Bill