Hand-wired core for ROM?

Not always (although your basic point, that in core ROM, a single core is often/usually used for more than one bit, is a very key point to note); the Apollo rope ROM had one core per 192 bits, or 12 words of 16 bits each, "thousands of ... cores" per memory rope. See: http://web.mit.edu/digitalapollo/Digital%20Apollo%20Annotated.doc and there's a picture of one here: http://klabs.org/mapld04/presentations/session_g/g1007_hall_s.ppt (see slide #15). Those notes do contain an interesting aside: "rearrange the program's fixed-memory allocations to avoid cases where such sets of 12 words contained too many ones to fit in their cores", which implies that the cores were fairly small, physically (since a one involved running the wire _through_ the core, not around it). I don't know why they didn't make the cores larger, and have fewer of them; my suspicion is that in manufacturing terms, it was easier to have more of them, with less wires through each one. (I can't think of an _electrical_ reason to do so; unlike with RAM cores, where smaller cores are faster to switch, and take less power to do so.)