The thread about the 'D' bolts started me thinking about mine. I have two bolts that can be used in my Inland. Both are 'round' and have no gas relief port. One is 'AI' - I know what it is but can never think of how to spell it - 'Autyere' (or something) for Inland. The other is 'OI' with a sideways serif '2', all markings on small lug. Who is 'O' in this case? The 'OI' is original blue, 50%, and the 'AI' is a very dark but not black matte finish. Both bolts have been inspected, gauged and test-fired. The 'AI' is actually the spare bolt.
