O V,
First question I have for your request for information is...
Does your carbine have Inspectors cartouche (may be more than one) on the left side of the wrist, just behind the carbine sling?
The cartouche will indicate it was indeed inspected and accepted into US Ord. Dept.
Without this cartouche, it may mean the arme was a private perches?
The date of manufacture maybe very difficult to guestimate. Those records just have not survived if they were ever kept at all.
Many arms after acceptance, were either in transit and/or kept in various destination points, some times for several months before they reached a safe destinations for issuance to the unit and/or troops.
I hope this helps.
My best,
Blair