lyman sights were not uncommon in those days
here on SN 1686 - very early made - target rifle

here are th holes on a M54J - “J” for jagt = hunting - cal. 7x61S&H, SN 2327

the rifle 2015 in poland

I have got this answer about it
"These holes are not on Mod. 65 - 65DL and 68DL"

probably the times were changing quickly in the 1960s.
scopes and scope mounts were expensive in 1954 more than most people had for a gun budget. its was completly different to our times and the lyman sight was cheap when the scope was expensive.

SN 396 and 522 get a new barrel now

new made 6,5x58RD reamer