Actually, some of the later versions of core memory were very difficult to see with a "naked eye"; almost grains-of-sand kind of thing. I own a couple of examp

Actually, some of the later versions of core memory were very difficult to see with a "naked eye"; almost grains-of-sand kind of thing. I own a couple of examples of core memory; one is a very old core assembly (I swear the frame is made of bakelite). It's highly damaged, missing several frames, and some of the existing "outside" frame have damage (but the inner frames are "ok"). Those cores are readily visible, and each measure a few millimeters in diameter (the wires of the grids are very thin magnet wire). There are around 10 or so layers in this core assembly (and I'm not sure how many were originally there). My other core assembly is a 16K board for some kind of a minicomputer or mainframe, made in the early 1970s. It even has a few surface mount components on it, plenty of thru-hole components, a few ICs (mainly line drivers), and the core memory module (which is actually protected by a metal cover - I've never opened it, so I don't know what it looks like underneath). My wife and I have it hanging in our dining area, next to our periodic table, stirling engine, and Tesla coil (yep). The whole board measures about 16 x 16 inches, and includes some metal frame stiffeners soldered on as well. The actual core assembly measures about 6 x 6 inches. In either of these, physical shock wouldn't do much (other things would break long before the core assemblies). That said, in actual construction they were typically protected in some manner; either in a case of some sort (in the case of the larger unit I have) or behind a metal plate (as in the board I have). This was mainly done to prevent fingers from poking where they shouldn't go (as well as prevent issues with tool slippage or dropping).