[Hugh]

Checked my two, & even tho they were made the same day or at least the same week, there is a difference in the "2 or 3 digit" placement:

SN 13310: last three digits on breechblock, rear toggle & grip safety,
last two digits on sideplate, bolt, trigger, middle toggle & grips.

SN 13398: last three digits on sideplate & grip safety,
last two digits on breech block, middle toggle, bolt, trigger, grips un-numbered.