This is the main plastic housing for the Lexus LS400 rear license plate lamp.  I took this off of a 1994 UCF21 Toyota Celsior, and it is the same part number used for 1995-1997 USDM Lexus LS400.  This part has been modified with a 15mm hole drilled in its center to accommodate a backup camera.

Note:  The OEM part number is an assembly that includes this plastic housing, along with mounting hardware, gaskets, lenses, bulbs, and sockets (pic included); the OEM assembly is discontinued and no longer available.  This auction only includes the the plastic housing (along with the upper gaskets, which are stick-on and in good condition), which was not sold separately; unlike this plastic housing, the gaskets (upper and lower), lenses, bulbs, and sockets also have their own part numbers and can be ordered online or through any Lexus dealer.