Need more help with identifying numbers please.

Could one of you gentlemen please tell be the meaning of this group of numbers?
https://www.milsurps.com/images/impo...cture067-1.jpg
They are on the bottom of this.
https://www.milsurps.com/images/impo...4_477711-1.jpg
Which is the 1941 Long Branch that I recently desporterised.
I was told earlier that the barrel was installed in 1961 while the rifle was in South African service but I neglected to ask about these numbers at that time.
Thank you for any help.