Ford Date Stamp on Part?

[AJB0009]

This is off of my 2004 Explorer, 4.0L.
It is a common, known issue that the harmonic balance separates and comes apart.
Vehicle has 140k miles on it. This balancer looks really good and I’m thinking that it has been changed, but not sure. That’s why I’d like to know the date on this part.
I bought the vehicle January 2018, so if it was replaced, it was prior to that. So, the 18 on the part isn’t the year.

 

[OVERKILL]

Per this very useful link: https://www.therangerstation.com/articles/how-to-decode-ford-part-numbers/

8L2E denotes
- 2008
- Explorer
- Engine Engineering

6B321 part number

RB (or AB, hard to tell) is the revision.