Back in the 1990s Harlequin Miniatures produced a licensed range of 28mm metal miniatures and I bought back a few of the blisters, including the robot mummy.
Having had a look at what was actually in the box of miniatures I found I had four of them.
The next stage after cleaning the metal miniatures was to give them a white undercoat.
Then a basecoat of very light brown, or ivory.