Philips PM5544 electronic testcard

[ppppenguin]

I can't be sure yet, but I think the core was designed as ROM, with the threading done accordingly. The Apollo Guidance Computer is an example.
https://en.wikipedia.org/wiki/Apollo_Guidance_Computer
https://en.wikipedia.org/wiki/Core_rope_memory

The first EPROM was introduced in 1971: https://timeline.intel.com/1971/the-worl...:-the-1702 This was about when the PM5544 was first marketed.