This is the underside of one of M56160's roof ventilators. As can be seen the bottom is pretty corroded, so it has been cut out, which will also allow the hole in the side to be repaired. A new solid base, which will blank the hole in the roof, has been cut from a sheet of aluminium. This will be sandwiched between the ventilator and roof, once the ventilator has been de-rusted and painted.
A few more dates have been added to M56160's history page.
... Much of the work in preserving these vehicles is done 'behind the scenes' so here is some of what is being done.