Hello Bruce.
When I was in Junior High School, the Father of one of my friends was an Illustrator who owned a sign shop. He had a lot of silk screen equipment in their basement, and I wish I had paid closer attention to it all at the time.
I do remember the screens were a two part item consisting of the thin fabric screen and a mask bonded to one side somehow. You cut the design through the mask and peeled away the bits you wanted the paint to pass through. The huge advantage of this printing technique is the design and any characters therein can be solid and continuous. By comparison, a stencil requires webs in the characters to hold them together. It would absolutely be possible to cut a silk screen mask that looked exactly like a stencil, but why?
Screening was definitely used with wireless equipment during the war. You can see it on any 19-Set Spare Parts Box, or Spare Valve Box, and if it is minty enough, you can often see the fabric shadow in the white paint under a low angle light.
Looking on the web today, there are a few commercial, line production stencilling machines available, but most seem geared to working with electronic circuit boards and other small, thin items of that nature. It is entirely possible these modern, compact machines evolved from much larger equipment from decades ago. We may never know.
Regarding the various boxes/cases for the 52-Set, I have photos of two different tool boxes with original markings, one in Canada and the other in England. The stencil markings on both are spot on identical in both form and location on the two boxes. I also have on hand, two Spare Parts Boxes and again, the stencil marking shadows are spot on identical in form and location.
In the pre-computer era, Sign Painters and Illustrators, were highly skilled positions and there was probably a lot of cross reference to other closely related skills like screening, stencil making and even engraving…all hand done. These physical skills are largely lost today. The station on the line for stencilling these boxes/cases was probably occupied by a lot more than just one person to keep production numbers up as you have noted. It would not surprise me at all if each work table was set up with jig options to hold the various cases/boxes in a specific spot, and perhaps even some form of mechanical arm which could swing the stencil down to the same spot for each type of case/box being worked on.
The viscosity of the paint is also critical. Too thin and it will wick under the stencils in a heartbeat. Too thick and it becomes hard to apply and you risk it drying out. Just right, and a skilled worker, and away you go!
Sorry for the length of this reply, Bruce. It amazes me what the older generations were able to accomplish with pure mind power and great hand/eye coordination and as much as I would love to know how they accomplished things like applying these markings, an answer may never be found. In the meantime, I shall muddle along and try and honour their collective skills as best I can. That probably means I end up drinking more than any of these workers ever did, but that is not a complaint…
David
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