Decoding "new to me" markings on a Springfield '03

[82Trooper]

Hello all.
Hoping someone can assist me with decoding one of the markings on a newly acquired 1903 Springfield . Based on the serial number, I believe it was manufactured in 1916.
Two questions tonight (more to follow!):
1.) The serial number is electro-penciled on the bolt....was this original? done when manufactured? or was it done later on at some point?
2.) There is a stamping on the butt stock that appears to read "3 GM - K"

As always, thanks in advance for those willing to share their knowledge.