I have some aircraft bolts that I am trying to use but I don't know what they are made out of. I figured out the last 2 digits are the diameter in 16th's and I think the letter before the last two numbers is the material. I figured out R is titanium but what is L,N,S & T. Thank you.
With diameter in Imperial units, the country of origin is more likely to be USA than France. For material, relative density (mass divided by volume) can give a good indication.