314.27(C) Floor Boxes. Boxes listed specifically for this application shall be used for receptacles located in the floor.
Exception: Where the authority having jurisdiction judges them free from likely exposure to physical damage, moisture, and dirt, boxes located in elevated floors of show windows and similar locations shall be permitted to be other than those listed for floor applications. Receptacles and covers shall be listed as an assembly for this type of location.
I have used some steel city stamped steel floor boxes with brass covers that where made for wood floor installation.
They where decent don't know the price.
