Winchester Carbine Serial Number Mystery

[Bubba-7]

Yea, looks like a 5.7 or 5.8. Are we to guess at the serial number? And why you think it is unusual?
NPM butt plate. I have seen two nice original looking Winchesters in the 6.4 range both with NPM butt plates, so I think it could be original.
So it could be a 6.4 or 6.5. The slide with a number would be latter than 5.8 and lead one to think it is a six million number.