It's a maker's mark / batch code just like the P60's have.
My first guess is the Arbeitsgemeinschaft für Osteosynthesefragen
or that the drop-in was made in Angola, which has the NATO country code of AO.
Hope this helps,
K
That's just what the One World Government wants you to think.but surefires are made in united states
My first guess is the Arbeitsgemeinschaft für Osteosynthesefragen