The reproof was 1954 - 1989. IF the original L barrel was '13' like the R that would be .710" - .718". When reproved the L barrel was .740" which is substantial honing.
The arrow is the date of proof code which I can't read.

[Linked Image from photos.smugmug.com]

3 tons/sq. inch would be the usual 2 1/2" proof; for a max. service load of about 9000 psi