Pretty Sure... But?

[sandasharpe]

OK Guys, anything else to add. What about the stamped vin?

[HK1837]

I wouldn't worry about it, the rest of the VIN is machine stamped on the assembly line. The PSN on these tags (which is the bit on yours stamped downwards) was sub contracted out by GMH, not stamped by GMH. The bits that are stamped properly are the bits that GMH stamped on the assembly line, so it has all been done right. My guess is they had lost the original tag, and being an 8/77 onwards Elizabeth assembly the BODY number on the BODY plate is the PSN, hence they couldn't just use another PSN tag like they could have prior to 8/77. So someone hand stamped a blank tag, then it got finished as per usual.
Remember also that this PSN places it close to the end of HX production, so if it was delayed for a short while which often they were it'd be finished during HZ production which may have something to do with it too.

[sandasharpe]

Thanks HK1837, this ties in with what others have told me but nobody could explain the stamped PSN

[HK1837]

Could also be an overtime shift car, and they couldn't find the PSN tag.