Nice photos. It's interesting that the boards shown use what look like carbon composition resistors, which drift high and out of tolerance with age. Makes it kind of surprising they were still operational.
"They were pieces of opaque adhesive tape, which was cut and meticulously applied to the foil by spatulae."
Actually the word you are after is scalpel. Various types used, but a small surgical scalpel with angled straight blade was best. The tape came in rolls. You'd stick down one end, run the trace by rubbing it down with a finger in the path you wanted, then cut the end-point with the scalpel. Pads came on backing sheets, and you'd use the scalpel point to lift one off the sheet, then place it down on the layout. With the scalpel under just one edge of the pad so you had a clear view of the grid sheet through the pad hole. The grid sheet was placed under the clear film used for the layout. The precision, stable, grid sheets were _very_ expensive. Typically the layout would be done at 4x final size, but you still used an optical loupe for best accuracy in tight spots.
Surprising to see that the pads and tapes are not falling off by now. The glue fails with age.
It's amusing the guy crossing off circuit diagram nodes and components as he laid the traces, didn't use any of that newfangled highlighter pen technology. Good old reliable pencil, that you can trust.
With all-new, computerized networked control systems at CERN, it will be interesting to see how long it takes some joker to sneak in stuxnet or whatever.