Different Leica M Seals

[Blind_spark]

I was just curious about the "L" seal and how different repairmen re-seal it. I just acquired a Leica M2 and it seems to have an "O" stamped into the wax. I previously owned an M3 and it had a "V" (roman numeral 5?). What might these things indicate? Just a curiosity, I know it has nothing to do with value. Thanks!