That battery powered memory approach sounds quite clever from the physical security perspective. It's so much scarier and more difficult to dump the key out of it. I guess it was too secure.

Many of the 2FA authentication solutions seem to have their own flaws and benefits. For example SMS 2FA though really weak against social engineering and vans under your window, it does not require a device which could be easily hacked over the internet, whereas the authenticator apps and hardware tokens are only recently catching up with on-device threats.