The Computer History Museum has on exhibit a rubylith mask for the 4K DRAM chip. According to the designer's oral history, they started using a Calcomp plotter to cut the rubyliths for the 4K DRAM while earlier ones were hand-cut.
It wouldn't have been possible to make the masks for the 4K chip by hand because hand-cut masks wouldn't be accurate enough. The problem was that the sense amps need to distinguish tiny voltage differences. If you cut the sense lines by hand, they would be slightly different widths, enough to mess up the signals.
The conference paper on this memory chip was authored by Schroeder and Proebsting of Mostek, so there were two main designers. There must have been more people on the team, but I couldn't find the size.
https://www.computerhistory.org/revolution/digital-logic/12/...
https://www.cs.utexas.edu/~hunt/class/2016-spring/cs350c/doc...