What does A. R. in A. R. sodium nitrite mean?
I don't know if I have completely answered, but here's my go:
AR : (ANALYTICAL REAGENT) : Reagents essential for analytical purpose and research work having high purity. If reagent meets the requirements of the American Chemical Society Committee on Analytical Reagents, it will be denoted as an AR (ACS) reagent.
Also see:

https://www.researchlab.in/?product-details/grade-of-purity/
https://www.avantorsciences.com/pages/en/grade-definitions#:~:text=AR%E2%80%94The%20standard%20Macron%20Fine,an%20AR%20(ACS)%20reagent.

EDIT:And note that it isn't a Analytical ring