Translate USERNAME To A Login ID

If anyone has some experience with this - would really appreciate some feedback.

We are on Lawson 9 - Windows Platform - Financials(AR)

In incidences where a given entry screen does not support inputting an overt Lawson "Operator" (AROPTR) - Lawson will write a windows-based ID to the USERNAME field(s).  EXAMPLE: Payment Batch/Header - ARPYMNTHDR.OPR_CODE  (NT00000023)

This appears to be a Lawson/Windows identifier - as in looking at tables in GEN (R_USER.USERNAME, QUEUEDJOB.USERNAME, USER_INFO.USERNAME, etc.) all reference this value.

I cannot, however, find any data (db tables) where I can rationalize this ID to a given user's login name. I want to be able to reference a table via this "USERNAME" to derive the user login ID.  NOTE: I have seen some references to a GEN_DB table of "USER" - but it is either not resident on my platform, or I can't see it for some reason.  Have also seen this USERNAME value reference as an "RMID" (Resource Management ID)

Appreciate your time in this matter.