No idea. For example, between the development of core memory and DRAM there were a host of technologies they tried because core is slow and expensive to manufacture. The best they did for speed was called thin-film, and they sold only two systems with it, upgrades of the System 360 Model 91 supercomputer named the Model 95. They had 1 MiB of it and 4 MiB of core, sold to NASA, the first Model 91 customer: https://en.wikipedia.org/wiki/IBM_System/360_Model_91