couple maybe over the years,,said have been done when the rifle was rebarreled, or after a rebuild,
each time a barrel was installed, a punch mark was made.
that doesnt wash, as iv seen a couple receivers that have never had a bolt fitted, or a barrel screwed in with a punch mark..
im guessing..
that if it was a rebarrel or major repair at one place,,ship, field ect, they got a punch,,
seems all the ones that have more then one punch have some of the same features,
iv also seen a 1917 Remington Enfield with the same punch marks, it had the original barrel still in it.