The good weather this weekend allowed the AWS air reservoir from 50211 to be recovered while it is accessible. Located below the floor, it wouldn't be visible when the cab is displayed anyway. It is identical to the reservoir on M56160, and so once tested and painted, will either be used to replace the existing reservoir (M56160's AWS hasn't been used in over 40 years, so the chances are it will need replacing) or held in stock as a spare.
M 56160's reservoir
... Much of the work in preserving these vehicles is done 'behind the scenes' so here is some of what is being done.