806 gearbox oil level?

I posted this question recently but the answer was not correct for my vehicle.. It was suggested the gearbox oil on an 806 turbo diesel (year

1997 ) is checked by identifying the larger bolt head on a ring of bolts on the gearbox extension cover accessible from the left hand wheel arch, where the bolt is the oil level plug. But my gearbox has a ring of bolts all the same size and believe the original suggestion must be for an earlier model.. I know my old 205 used that method .So, if anyone can advise me the correct method I would be very thankful. Thanks in advance. KF.