Definitely the cover for getting to the fuel gauge sending unit. I know the 60 has this too. Just too bad they didn't put one in to access the fuel pump on the FJ62. Guess the 3FE market was small enough didn’t think it was worth necessary. In twenty-nine years owning my 89 FJ62 I've had to drain and lower the fuel tank twice to replaced the pump. Fuel gauge sending unit on the other hand still works fine.