Here's a core memory plane I bought a few years ago. This is a 4096 bit plane from an early-'60s Univac 418:
Full size close-up:
"I had always believed that first came the vacuum tube, then the transistor, period. But thanks to an old Navy tech manual sent in by a reader, I've discovered a third "lost" entity. This document, unusually passionate and well written for a military tech manual, is their promotional brochure..."
I once had to replace a defective memory assembly -- the end of messages in the system were indicated with 4 N's in the first few columns ("NNNN") and one of the cores went bad so the N in that column was never recognized (the other characters in that column were munged too), and so the message never ended. Over a day with an oscilloscope to find that one bad core and convince the NCOIC that I was right... I didn't have a microscope, but to the naked eye the core looked fine. It just wasn't flipping like it should have.
It had a core memory when it was initially deployed.
At a later base I was at, they were installing the then-new X.400 system . It didn't last long, as SMTP ate it's lunch. Which is funny, as I got to watch an IMP  get installed by the BBN  contractor that same year.
Apollo Guidance Computer (the computer of the Apollo Command Module) has 36K 16-bit words of core rope memory. That is about 0.5MB. There were at least ten such computers created. So, this much core rope memory was woven for the Apollo Command Module's computers alone. See a previous discussion:
It shows how hard it was to make a memory device in the 1950s. For a long time, that was the bottleneck in computing. Electronic arithmetic units date from around 1940, but memory devices that didn't suck only came in around 1965, and didn't get cheap until around 1990.