It sounds like you’re asking about the (a slim internal Blu-ray drive) and possibly a “hot” or unofficial/beta flash, or the “BU40N 1.00” firmware used for enabling LibreDrive or UHD ripping.
Firmware version 1.00 is considered the "holy grail" for the LG BU40N (and rebadged versions like Archgon or Verbatim slim drives). bu40n 100 firmware hot
For users of the slim internal Blu-ray drive, the 1.00 firmware It sounds like you’re asking about the (a