Do these numbers mean anything?NOOB

[84GNPILE]

What do the numbers/letters mean that are inside the inked? circles on the fins of the turbo mean?

Mine has 97/2Y in one circle, and AO/106 in the other.stk housing, plate on the back stamped Factory Overhauled Turbocharger.Allied Signal, and Garrett, and serial #

 

[84GNPILE]

47 Views, no replies..........Must be one of the great GN mysteries