You can just imagine how Mr Vincent felt when sets of C/cases all machined up bolted together, blanks put on all the apertures, then submerged in water and an airline connected to pressurise the C/cases, then they revealed if they were porous or not before filling them up with parts, He had literally hundreds of them until they devised a way to seal them with shellac by putting them in a vat of it and pulling a vacuum sucking out the air then releasing it and the shellac was drawn into the cases. after cleaning and all threaded holes re-tapped yellow chromate was applied on the outside then stoved enamelled, he told me he didn't make much on shadows as the work involved was so much. Typical manufacturer, having a poor product which he had to sell, made in go faster adding a few choice distinctive components. It was certainly an experience meeting him so often as I did with the stem of bananas and an Ltr bottle of whisky, only ever taking a couple of hands of bananas but always kept the full bottle of whisky.
Never painting "D" cases as they didn't require it die-cast.